All of the names I thought of for this have been absurd and long. Like “zero-knowledge reciprocal crush verification.” That was the cutest example. Say that person A has a crush on person B. However, A doesn’t want to face public rejection or other social repercussions of telling B. This method shows how A can see if B feels the same way.
A sends a note to B via a disposable email account or note in a locker or other untraceable means. The note says:
“I have a crush on you. Find me. Around people you have feelings for, use the word relinquish* in conversation. For those you don’t like in that way, use the word vanquish*”
I actually first imagined this when considering how to pose a sensitive question to a public figure, such as one about religious affiliation. In this example, the commoner sends a letter like this:
“Are you an atheist? If so, use the word vanquish (as in, vanquish all thought of superstitious nonsense) in one of your speeches or interviews, but if not, use the word relinquish (as in, I relinquish my soul to God).”
* Any two obscure words can be used.