Tail over teakettle is one of several similar phrases to describe a tumble or fall But where/how did this originate A few web searches give me pages where people use the phrase, and one of the He is getting the brunt of the joke He is getting the raw end of the deal He got the business end of a sword
Someone who continually gets the joke butts can be referred to as a butt monkey but that may be returning to using butt to mean your tushy. The connection between the baby and the spank on the tushy is pretty well engrained in the american psyche, i believe By the way, another americanism is as cute as a baby's bottom, (or sometimes smooth as a baby's bottom) which adds another wrinkle to the notion of brand spanking newness.
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