I've heard the phrase "forming an algebra" being used for delaying effects by means of recording the intents into a data structure. So for instance a function which initially performs file i/o as a side effect, could instead return a data structure "FileOperations" with entries like "FileWrite(a.txt, Hello world)".

Maybe that's where they got the name from? Although performing the effects directly through a pause/resume mechanism doesn't sound algebraic to me.