First off, we have à la mode. When LL lived in the US, she thought it hilarious (and still does) that a French phrase meaning 'in the current fashion' could come to mean 'with ice cream', as it does in AmE in pie à la mode or pancakes à la mode (as ordered in the recent and wonderful film Little Miss Sunshine). A situation involving ice cream may also be described as à la mode in AmE:
One item on the Blue Bunny ice cream parlor menu, however, has never been purchased. It's called Sock Hop a la Mode.So, how did à la mode come to mean 'with ice cream'? Various stories circulate, but the most 'official' of these is that Charles Watson Townsend introduced pie à la mode to Delmonico's restaurant in New York (having dubbed a pie thusly at an upstate restaurant) in the 1890s, and it took off. You can read more of that version of the story here.
You and 25 of your friends can rock around the clock at a sock hop at the ice cream parlor, complete with '50s music, decorations and all the ice cream sodas and treats you can eat. --USA Today, 25 July 2003
So, that's Americans doing strange things with a French phrase. Now we come to the British doing odd things with a Latinate word. LL e-mailed me (BrE) in/(AmE) during the week to ask whether prevaricate really means 'to hesitate' in English. Knowing the cognate Italian word, LL believed the word to mean 'to evade or deviate from the truth'. That's what I believed the word to mean too, until I encountered it as used by my UK students, who use it as a synonym for procrastinate. This meaning is not considered to be standard--and many dictionaries do not record it, but some (e.g. Penguin) and some style guides acknowledge that the sense is 'out there' in BrE mouths and minds, and try to fight against it.
Incidentally, prevarication, i.e. using a communication system to deceive, is one of the Design Features of Language--that is, one of the hallmarks indicating that a communication system is a language.