What does the T stand for in "T flip-flop"?
Some people believe that the &quot;T&quot; in &quot;T flip-flop&quot; stands for &quot;toggle,&quot; but I believe that it originally was intended to stand for &quot;trigger.&quot;
According to the Wikipedia entry on flip-flops,

According to P. L. Lindley, an engineer at the US Jet Propulsion Laboratory, the flip-flop types detailed below (SR, D, T, JK) were first discussed in a 1954 UCLA course on computer design by Montgomery Phister, and then appeared in his book Logical Design of Digital Computers.[10][11] Lindley was at the time working at Hughes Aircraft under Eldred Nelson, who had coined the term JK for a flip-flop which changed states when both inputs were on (a logical &quot;one&quot;). The other names were coined by Phister.

In Montgomery Phister Jr.'s book Logical Design of Digital Computers (New York: John Wiley &amp; Sons, Inc., 1958, pp. 126-127), he states

The T Flip-flop
The T or trigger memory element has a single input line which causes the memory element to change state when it is &quot;one,&quot; but leaves it in its former state otherwise.

Because it seems that Phister was the first one to use the term &quot;T flip-flop&quot; and he used the &quot;T&quot; to stand for &quot;trigger,&quot; it seems that this is what it was originally intended to mean.