Why are flip-flops (bistable memory devices) called flip-flops?
The Wikipedia entry for flip-flop says that the terms "trigger circuits" and "multivibrators" were used in the past but not the justification for the term "flip-flop".
Electronic – Why are they called flip-flops
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Related Solutions
This terminology goes waaaaay back to the days of vacuum tubes.
Generally, you would mount a number of tube-sockets on standoffs to a piece of wood (the actual "breadboard"), and do all the wiring with point-point wire and the components just hanging between the various devices.
If you needed additional connection points, you would use a solder-lug terminal strip.
Image credit: Random googling.
The story goes that an engineer had an idea for a vacuum tube device late one night. Looking around the house, the only base for his prototype that he found was indeed his wife's breadboard, from the breadbox.
Now, I'm not endorsing actually using a real breadboard. It's your marital strife if you do.
I've actually constructed a tube project using the breadboard technique. It works very well.
To make a T flip-flop, you take a D-flip flop and add feedback from the output to determine the next state.
The immage bellow shows the most basic operating logic of a T flip-flop. If you removed the feed back from Q and Q' you get a D flip-flop (And I know, you also have to invert the bit input on the lower and gate. Lets keep it simple, ok?)
So when you go to use a D flip-flop in a counter circuit instead of a T flip-flop, you have to manually add in the feedback that is now missing.
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Best Answer
I had always assumed that it was just because they flipped states. And flop may refer to the optional reset (causing the circuit to flop). But, looking into a bit more ...
From the online etymology dictionary:
"Flip-flop in the general sense of "complete reversal of direction" dates from 1900; it began to be used in electronics in the 1930s in reference to switching circuits that alternate between two states. As a verb by 1897. Flop (n.) in the sense "a turn-round, especially in politics" is from 1880."
A flip flop is generally used to hold a binary value. The "complete reversal of direction" is a good root (since a 0 vs 1 are opposites of one another).
Another illustrative general definition of flip flop: "To alternate back and forth between directly opposite opinions, ideas, or decisions." This lends itself to binary representation well.
So looks like the word existed before the electronic device.