I was recently watching an old episode of The West Wing, and a character was recounting a story from his youth. He said “I was babysitting for my sister”. It eventually became apparent that he meant he was caring for his sister while his parents were away.
In Canada (or at least on this coast), we would say “I was babysitting my sister”. If we added the “for”, it would imply that we were replacing the sister as babysitter or caregiver, as in “I was caring for children on my sister’s behalf”.
When I lived in Ireland, an American colleague and I were confused by an email from a British colleague. He said something like “let’s table that discussion”. We wanted to talk about the issue, so we were taken aback. We eventually discovered that the verb ‘table’ means opposite things on opposite sides of the Atlantic.
Being writers, we even came up with a term for this rare phenomenon:
dialectal self-antonym – Applied when a word has opposite or wildly divergent meanings depending on which country or region it is used in. For example, in Britain the verb “to table” means to “add to an agenda” while in North America it means “to remove from consideration indefinitely”. For another example, the adjective “homely” when used in North America is applied to a person who is “plain or unattractive in appearance”. In Britain, the same word is used to mean “comfortable or cozy, like at home”.
This may win the prize for least cool post of the month. But then, the month is still young.