The usages of ass vs. arse are varied, but the etymology was fascinating.
“Arse,” meaning buttocks, is a very old word, listed in the OED as being first used in AD 1000. “Ass” is just as old as a word, but it meant “donkey” up until 1860, when the OED first cites it as meaning “buttocks.” It was first used as a euphemism; “arse” was too vulgar for polite society, so “ass” was used instead. “Arse” fell out of use and “ass” became the vulgar word.
In the 20th century, “arse” was revived as a less vulgar term for “ass.” It thus became a euphemism for itself.
So how is arse pronounced? The way I always heard it (which is seldom in the US) was with an ‘a’ sound similar to that in car or father. The pronounciation guide in my dictionary seems to agree. A long ‘a’ sound here is more like that in cake.
Along with arse and shite, where does a word I heard in the movie Formula 51 fit in. I believe the word was bollocks, but I guess it could have been bullocks. Any help on that one?
It’s an “ah” sound. Which one it is isn’t always easy to pin down in writing.
The long vowel/short vowel terminology used in American schools, frankly, sucks, and it always confuses the issue. No one who knows anything about phonetics would call the “a” in “hat” the “short a” and the “a” in “hate” the “long a.” Those are two completely different sounds – one an unrounded low front vowel ([&] in ASCII IPA) and the other a diphthong ([eI]). “Long” simply means longer than “short,” not a completely different sound.
Taking into account the different vowel sounds in English English and North American English, and also the question of how much, if at all, you pronounce the R, I reckon you cannot go far wrong if you pronounce Arse the same as you would pronounce Farce.