Heard a kid call a speed square a "triangle ruler" last week... it took me a second to even figure out what he meant. My old foreman had a name for every tool in the box, stuff you'd never find in a catalog. Makes you wonder what gets lost when the old guys retire.
My uncle was a carpenter for forty years and he called it a triangle ruler too. That kid might have picked it up from an older guy on his crew. Sometimes the weird names stick around more than the official ones. I don't think the knowledge gets lost, it just changes hands with a new nickname. The important part is if he knows how to use it to mark a cut.