I'm rather interested in the history of eletrical engineering, and I've seen some discussion here and there about the origin of the names of the various flip flop circuits. Some time ago I took part in one such discussion here: Understanding D flip flop function - what this thing does, and became so interested on the subject that I purchased an early textbook from 1957, which supposedly is the first university level textbook where flip-flops are discussed.
I promised to report my findings, and I'll do so below. But sadly it didn't answer all my questions. It seems that using flip flops was already an established tradition in 1957 and the book doesn't discuss any history. So please answer if you have any info on the subject.
So I am looking for references that predate 1957. I am also interested in the origin of the characters J and K in a JK flip-flop, in case someone would be able to verify or clarify the answer given in What is the meaning of JK flip flop's J and K ?.