In semaphore, why doesn’t the letter J follow the pattern? One would expect J to be depicted by the position of K (then K would be the position of L, etc.)
There actually seem to be at least four “out of sequence” letters – J. V, W and X – and my guess is that for whatever reason they were left out at first as not being needed, then were later tacked on, much as the signal flags used for the alphabet by the International Code of Signals omitted the vowels in their original incarnation.
In any event, the practice goes back at least 100 years, as my 1909 edition of “International Code of Signals: American Edition” lists this sequence of signals as “The British Method of Semaphoring by Hand Signals”. This book also includes an entry for the “French Method of Semaphoring by Hand Signals” which was more regular, although for some reason it omits W, with the notation to send two-Vs for W.
If in sequence, V would be the same as Cancel and W would be the same as J. X seems to follow W logically. (i.e., the left hand goes from 3 o’clock to 4:30.)
I don’t know much of anything about semaphores, but it may help to know that in french, W isn’t “double-u”, it’s “double-v”.