Why do we call it a “washing machine” but not a “dryer machine”? Yes, it’s a machine, but we just call it a dryer. It struck me as odd this morning while looking at it. And why, when we refer to both, it’s “washer and dryer,” but on its own, it’s “washing machine”?

Also, why do we say “hot water heater”? The word heater already implies hot water. Why not just “water heater,” “hot water,” or simply “the tank”? (Thanks to Laura Kern for that insight.)