Official Name for the “First” Programming Language Developed by Turing?
Turing machines are not programmable. Each Turing machine computes only one function. Hence they do not use any
programming language. What you see as a language is the description of
the machine itself, not of a program in some programming language. Thus the name "Turing machine" is the only appropriate terminology.

Now it turns out that there are devices that can emulate Turing
machines, such as a computer programmed to do such an emulation.  They
can use the description of a Turing machine to simulate its
computation. This is very similar to a hardware emulator that can
mimic the hardware of a computer from a formal description of the
circuits.

The abstract theoretical model of such an emulation, as then performed
by a Turing machine is called a Universal Turing machine. But
universal Turing machines are in no way specialized for that kind of
description. It is a much more general concept. The most general name for the input to a universal Turing machine could possibly be "Natural numbers".

However, in his 1936 paper On Computable Numbers, with an Application to the Entscheidungsproblem, Turing uses the kind of encoding you have in mind as input to be properly encoded for his universal computing machine.
He calls it "standard description", abbreviated as "S.D.".

But it is not the first Turing complete language, even ignoring earlier theoretical work such as done by people like Church and Gödel.

You view of history is missing an earlier invention, which is Charles Babbage's Analytical Engine. Lady Augusta Ada King, Countess of Lovelace, is considered the first programmer in history, though her computer, Babbage's engine, never worked in her lifetime. I do not know that the "assembly language" for the engine received a name. According to Wikipedia it would have been Turing complete.