B-U-T and T-U-B
Somewhere around 60 years ago, according to Zeddie Gillenwater of Sumerco, a woman sold her tobacco crop and, with a stack of bills in her hand, headed off to the store to buy a good, wood-burning stove.
"We have several different makes and sizes," the clerk said. "About what BTU did you have in mind?"
"Yes, ma'am. That's a unit of measure, a way to measure heat."
"Well, I don't know nothin' about B-T-U. All I want is a stove big enough to heat a B-U-T as big as a T-U-B."