In the Greenville section…
In the Greenville section of Jersey city we used the word “fins”. We called it “finsey” pronounced fins-ee and crossed our fingers as well. I learned that the word came down word of mouth from generation to generation from jousting. If the champion wanted to take it easy on his losing opponent, the champion would “feign” an injury so that his opponent could take a face saving break to rest and recover. An example of the strong giving deferring to the weak.
Calling “fins” was always honored. It was in fact the honorable thing to do because all the players who let us call “fins” became, like the champion jousters, the chivalrous ones.
Coming down through word of mouth for over 400 years from older kids to younger kids in street play, a word like “fins” is referred to as a meme.