Output programming language name
Outputs to STDERR
Outputting to STDERR is now at +33/-21 as an allowed default, which is positive but contested. This is a CW answer to collect answers that just invoke an error in a language where error messages includes the language name.
Haskell, 1 byte
1

Error:
Parse error: naked expression at top level
Perhaps you intended to use TemplateHaskell

Lua, 1 byte
1

Error:
lua: .code.tio:1: syntax error near &lt;eof&gt;

(file name is unimportant)
Batch, 1 byte
~

Error:
'~' is not recognized as an internal or external command,
operable program or batch file.

tinylisp, 5 bytes
(c()1

Error:
Error: cannot cons to Int in tinylisp

R, 1 byte
)

Error:
Error: unexpected ')' in &quot;)&quot;

Java bytecode, 0 bytes
Error:
Exception in thread &quot;main&quot; java.lang.ClassFormatError: Truncated class file

Groovy, 1 byte
a

Note that a can be replaced with any other character
Error:
groovy.lang.MissingPropertyException: No such property: a ...

MATLAB, 1 byte
\

Error:
Error: Unexpected MATLAB operator.

PHP, 3 bytes
&lt;?=

Error:
PHP Parse error:  syntax error, unexpected end of file in /home/runner/.code.tio on line 1

CJam, 1 byte
/

Error:
/
^
RuntimeException: The stack is empty
Java exception:
java.lang.RuntimeException: The stack is empty
    at net.aditsu.cjam.CJam.pop(CJam.java:75)
    at net.aditsu.cjam.Op2.run(Op2.java:10)
    at net.aditsu.cjam.Block.run(Block.java:304)
    at net.aditsu.cjam.CJam.runCode(CJam.java:210)
    at net.aditsu.cjam.CJam.main(CJam.java:240)

Twig, 2 bytes
Twig is a template language written in PHP. It's possible that this is a polyglot.
{{
{%
{#

Error:
PHP Fatal error:  Uncaught exception 'Twig_Error_Syntax' with message [...] in [...][...]:n:
Stack trace:
#0 [...]

The message varies depending on which program you choose.
[S.I.L.O.S], 2 bytes
x+

[Try it online!]
[S.I.L.O.S]: https://github.com/rjhunjhunwala/S.I.L.O.S
[Try it online!]: https://tio.run/nexus/silos#@1@h/f8/AA &quot;S.I.L.O.S – TIO Nexus&quot;
Trivially invokes undocumented behavior. Silos is the name of the language.
Python, 6 bytes
pYTHON

As the character restriction is case insensitive, and the output doesn't have to be in the correct case, this is a valid answer. The error message it produces is something like this:
Traceback (most recent call last):
  File &quot;.code.tio&quot;, line 1, in &lt;module&gt;
    pYTHON
NameError: name 'pYTHON' is not defined

Try it online! (outputs to 'debug' tab)
JavaScript, 10 bytes
jAVAsCRIPT

This produces the following error message or similar in all environments:
ReferenceError: jAVAsCRIPT is not defined

QBIC, 6 bytes
?b(12)

In 6 bytes, we can put QBIC encountered error: 9 on the screen, signifying an out-of-bounds error.
ForceLang, 2 bytes
()

Error produced:
Exception in thread &quot;main&quot; lang.exceptions.IllegalInvocationException: null is not a function.
    at lang.ForceLang.parse(ForceLang.java:99)
    at lang.ForceLang.main(ForceLang.java:129)

Pip, 5 bytes
1~`[`

(Note: this works in the current version as of this writing, 0.17.09.01. No guarantees the interpreter won't change to handle this error differently in the future.)
Tries to regex match with a syntactically invalid pattern. The error produced will look something like this:
Traceback (most recent call last):
  File &quot;/opt/pip/pip.py&quot;, line 221, in &lt;module&gt;
    pip(interactive=False)
  File &quot;/opt/pip/pip.py&quot;, line 206, in pip
    state.executeProgram(tree, args)
  File &quot;/opt/pip/execution.py&quot;, line 56, in executeProgram
    returnVal = self.functionCall(mainFunction, cmdLineArgs)
  File &quot;/opt/pip/execution.py&quot;, line 368, in functionCall
    returnVal = self.getRval(returnExpr)
  File &quot;/opt/pip/execution.py&quot;, line 235, in getRval
    expr = self.evaluate(expr)
  File &quot;/opt/pip/execution.py&quot;, line 213, in evaluate
    result = opFunction(*args)
  File &quot;/opt/pip/execution.py&quot;, line 1134, in FIRSTMATCH
    matchObj = regex.asRegex().search(str(string))
  File &quot;/opt/pip/ptypes.py&quot;, line 175, in asRegex
    self._compiled = re.compile(pyRegex)
  File &quot;/usr/lib64/python3.6/re.py&quot;, line 233, in compile
    return _compile(pattern, flags)
  File &quot;/usr/lib64/python3.6/re.py&quot;, line 301, in _compile
    p = sre_compile.compile(pattern, flags)
  File &quot;/usr/lib64/python3.6/sre_compile.py&quot;, line 562, in compile
    p = sre_parse.parse(p, flags)
  File &quot;/usr/lib64/python3.6/sre_parse.py&quot;, line 855, in parse
    p = _parse_sub(source, pattern, flags &amp; SRE_FLAG_VERBOSE, 0)
  File &quot;/usr/lib64/python3.6/sre_parse.py&quot;, line 416, in _parse_sub
    not nested and not items))
  File &quot;/usr/lib64/python3.6/sre_parse.py&quot;, line 765, in _parse
    p = _parse_sub(source, state, sub_verbose, nested + 1)
  File &quot;/usr/lib64/python3.6/sre_parse.py&quot;, line 416, in _parse_sub
    not nested and not items))
  File &quot;/usr/lib64/python3.6/sre_parse.py&quot;, line 523, in _parse
    source.tell() - here)
sre_constants.error: unterminated character set at position 8

Stax, 2 bytes
0u

Error:
Stax runtime error: rational divide by zero

zh also works.
###ink, 1 byte
~

~ at the start of a line marks that the line is a statement to be executed, rather than text to be printed. As of whichever version of inklecate TIO is using, if there's nothing after the ~, the interpreter crashes with the following error:
System.NullReferenceException: Object reference not set to an instance of an object
  at Ink.InkParser.LogicLine () [0x000b1] in &lt;b1e5e74f4ee842fc961297862cf23e07&gt;:0 
  at Ink.StringParser.ParseObject (Ink.StringParser+ParseRule rule) [0x00012] in &lt;b1e5e74f4ee842fc961297862cf23e07&gt;:0 
  at Ink.StringParser.OneOf (Ink.StringParser+ParseRule[] array) [0x0000a] in &lt;b1e5e74f4ee842fc961297862cf23e07&gt;:0 
  at Ink.InkParser.StatementAtLevel (Ink.InkParser+StatementLevel level) [0x00009] in &lt;b1e5e74f4ee842fc961297862cf23e07&gt;:0 
  at Ink.InkParser+&lt;&gt;c__DisplayClass134_0.&lt;StatementsAtLevel&gt;b__0 () [0x00000] in &lt;b1e5e74f4ee842fc961297862cf23e07&gt;:0 
  at Ink.StringParser.ParseObject (Ink.StringParser+ParseRule rule) [0x00012] in &lt;b1e5e74f4ee842fc961297862cf23e07&gt;:0 
  at Ink.StringParser.Interleave[T] (Ink.StringParser+ParseRule ruleA, Ink.StringParser+ParseRule ruleB, Ink.StringParser+ParseRule untilTerminator, System.Boolean flatten) [0x00040] in &lt;b1e5e74f4ee842fc961297862cf23e07&gt;:0 
  at Ink.InkParser.StatementsAtLevel (Ink.InkParser+StatementLevel level) [0x0004f] in &lt;b1e5e74f4ee842fc961297862cf23e07&gt;:0 
  at Ink.InkParser.Parse () [0x00000] in &lt;b1e5e74f4ee842fc961297862cf23e07&gt;:0 
  at Ink.Compiler.Compile () [0x00033] in &lt;b1e5e74f4ee842fc961297862cf23e07&gt;:0 
  at Ink.CommandLineTool..ctor (System.String[] args) [0x001a3] in &lt;d64e27e7788347b2a5377c9e19bbdcab&gt;:0 
  at Ink.CommandLineTool.Main (System.String[] args) [0x00000] in &lt;d64e27e7788347b2a5377c9e19bbdcab&gt;:0 
[ERROR] FATAL UNHANDLED EXCEPTION: System.NullReferenceException: Object reference not set to an instance of an object
  at Ink.InkParser.LogicLine () [0x000b1] in &lt;b1e5e74f4ee842fc961297862cf23e07&gt;:0 
  at Ink.StringParser.ParseObject (Ink.StringParser+ParseRule rule) [0x00012] in &lt;b1e5e74f4ee842fc961297862cf23e07&gt;:0 
  at Ink.StringParser.OneOf (Ink.StringParser+ParseRule[] array) [0x0000a] in &lt;b1e5e74f4ee842fc961297862cf23e07&gt;:0 
  at Ink.InkParser.StatementAtLevel (Ink.InkParser+StatementLevel level) [0x00009] in &lt;b1e5e74f4ee842fc961297862cf23e07&gt;:0 
  at Ink.InkParser+&lt;&gt;c__DisplayClass134_0.&lt;StatementsAtLevel&gt;b__0 () [0x00000] in &lt;b1e5e74f4ee842fc961297862cf23e07&gt;:0 
  at Ink.StringParser.ParseObject (Ink.StringParser+ParseRule rule) [0x00012] in &lt;b1e5e74f4ee842fc961297862cf23e07&gt;:0 
  at Ink.StringParser.Interleave[T] (Ink.StringParser+ParseRule ruleA, Ink.StringParser+ParseRule ruleB, Ink.StringParser+ParseRule untilTerminator, System.Boolean flatten) [0x00040] in &lt;b1e5e74f4ee842fc961297862cf23e07&gt;:0 
  at Ink.InkParser.StatementsAtLevel (Ink.InkParser+StatementLevel level) [0x0004f] in &lt;b1e5e74f4ee842fc961297862cf23e07&gt;:0 
  at Ink.InkParser.Parse () [0x00000] in &lt;b1e5e74f4ee842fc961297862cf23e07&gt;:0 
  at Ink.Compiler.Compile () [0x00033] in &lt;b1e5e74f4ee842fc961297862cf23e07&gt;:0 
  at Ink.CommandLineTool..ctor (System.String[] args) [0x001a3] in &lt;d64e27e7788347b2a5377c9e19bbdcab&gt;:0 
  at Ink.CommandLineTool.Main (System.String[] args) [0x00000] in &lt;d64e27e7788347b2a5377c9e19bbdcab&gt;:0