"Origins of words" by Susie Dent, Countdown 10/10/17 (lieutenant, could, pease)

I have to thank Kevin Loughran, I think is how he pronunces his name. He e-mailed in to say, "Is that any reason, historical or otherwise, why we pronounced lieutenant with an F sound?" It's some of the big riddles of English. It's true. In the normal British pronunciation, of course, we do say "leff-tenant"whereas in America they say "lou-tenant", which seems much more plausible. WE're not completely sure where the British pronunciation came in but our most plausible guess, really, is that at some point before the 19th century, when it began to change, the U at the end of the Old French, lieu, was read and pronounced as a V. This may have been done simply because it was easier to pronounce because lieu doesn't exactly trip off the English tongue. But it may also have been done in error. Vere often these errors happen by association. There was another word around at the same time and that was lief, and that was used as a term of address, particularly towards a superior. So it may be that somehow in the heads of English speakers the lief got mixed up with the lieu and the "leff" crept in to the lieutenant. So I hope that answers Kevin's question. As I say we can't be completely sure, but that's our best guess. I talked about mistakes in English etymology, which that may have been an example of. There are quite a few, in fact. The could in the past tense of can, that never had an L originally. That just crept because shall ans will kept their Ls in the past tense so we shoved one in could, as well. Similarly, pease, we used to have pease pudding. We thoughtif you have a lot of pease, you must be able to have one pea. So we kind of invented our own singularity in that case. So many, many examples in English where we've got someone slighlty wrong in the past and we're left with a result.