"ETA"

I've noticed a lot of livejournallers using this term to denote a later edit to an entry. Where does it come from, and how is one supposed to read it to avoid "Estimated Time of Arrival"?

If you don't know, and you have a friend who uses it a lot, ask them! If you do know, or want to make up an amusing reason for it, post it! If you don't know and don't have any imagination, post saying so!