I always assumed this was some old crusty project management term that predated modern technology but the Wikipedia sphere says it was coined in the late 80s by Ivar Jacobson of Ericsson in the context of requirements analysis.  Apparently the original Swedish term is "användningsfall".  I've got a coworker that likes to share "fun facts" every Friday...I might have to supplement that bit of our call tomorrow :)

- Matt G.