This evening I got home in time to see part of Jeopardy, and the Final Jeopardy question was something about how certain birds tricking other birds into rearing their young led to this term relating to infidelity. (Apologies for not recalling the exact text of the answer.)
I blurted out the answer--er, the question--almost immediately.
None of the three contestants even came close to getting it.
I did my little victory dance, right there in the living room. Oh yeah! I knew something the supposed brainiacs didn't. Or at least for some reason my brain thought of that at the appropriate time (it only works like this when it does me absolutely no good, however).
The "question": Cuckold. It comes from (believe it or not) the cuckoo bird, which would lay eggs in the nests of other birds.
Yes, I really should have better things to tout in my life.