On StackExchange, someone asks why programmers talk about “calling” a function. Several possible allusions spring to mind: Calling a function is like calling on a friend — we go, we stay a while, we come back. Calling a function is like calling for a servant — a summoning to perform a task. Calling a function is like making a phone call — we ask a question and get an answer from outside ourselves. The true answer seems to be the middle one — “calling” as in “calling up, summoning” — but indirectly, originating in the notion of “calling for” a subroutine out of a library of subroutines in the same way that we’d “call for” a book out of a closed-stack library of books.