Until this thread, I’d never heard it, period. I’ve lived all over the southeast US, by the way.
The term “strictly speaking” presumes that the dictionary may offer contradictory, ambiguous, or confusing alternative definitions.
About Ireland, you’re right about the song lyrics, but in Dublin, the big roads going along the edges of the river Liffey are the Quays…pronounced Keys.
Outside of the gaeltacht and people speaking Irish, the word "Quay " is always pronounced “Key”.