"hot water heater."
Glenn, this seems to be a Southern, or possibly Texas thing. I've heard it and said it all my life. Note builder's and my locations. Then one day I heard my self and stopped in midsentence, "Hold on there," I sez, "that don't make a lick of sense." None the less It still slips out some time. But then who wants a cold water heater, I reckon that melts ice to give you cold water.
Hot water heater may be a carry over from when water was heated in a boiler, either dedicated or part of wood, coal, or "coal oil" stoves then stored in a hot water tank. When the new fangled water heaters came along the hot prefix just stayed attached.
[CENTER][FONT=Comic Sans MS]Measure twice, cut once.[/FONT][/CENTER]
[CENTER][FONT=Comic Sans MS]Look at the nail, not the hammer. Watch the fence, not the blade.[/FONT][/CENTER]
[CENTER][FONT=Comic Sans MS]If you hook your thumb over your belt you won't hit it with the hammer or leave it layin on the saw table.[/FONT][/CENTER]