Floor based WSJ reporter Clifton Linton wrote the above 1995 WSJ article on how ubiquitous hand signals were for those who worked around the trading pits in Chicago. The article also captures how hand signals permeated the lives of floor personnel which lead to uses in other aspects of life, including a comment by a trader's wife who mentions that her husband doesn't talk in his sleep but unconsciously uses hand signals, LOL.
One note I'll add is that at the end of the article it mentions the bar Cactus which was enough of a trader hangout that it's original domain address was dontdrinkandtrade.com