adding to recent discussions...

...on the difference between "ass" and "arse" and why it is so important to retain the english usage of "arse" rather than translating it to the american "ass" - because if you change "arse" to "ass", then the following definition does not work:
arsenic: to steal buttocks

(With all due ackowledgement, respect and indebtedness to Graham Garden* who used this defintion in the round of Uxbridge English Dictionary just broadcast as part of the Humph Celebration Concert on BBC R4)

*I think it was him, if not please correct me in the comments.