It is a foible of mine that I am a connoisseur of etymology and of historical sound changes, and that I like to reconnoitre them – and write about them.
Foible? In truth, it’s as much a strength as a weakness, isn’t it? I mean, you’re here reading this, after all. But perhaps you don’t think of foible as a synonym of weakness, not quite. More like quirk or silly detail or something like that – after all, it has the oi that shows up in springy words like boing and less pleasant words like oily and moist, plus the ble that shows up in wobble and quibble and, um, feeble…
Feeble? Ah, hello, meet your long-lost twin, foible. Yes, these two words are doublets, peeled apart by the fallibility of historical language change – oh, hello, fallible, you’re at a different table, sorry. Oh, don’t cry! That’s our business at this table.
Feeble and foible, you see, are alternate forms of the word that came from Latin flebilis, which meant ‘weepable’, i.e., ‘to be wept over’. That in turn came from fleo, ‘I weep’, which traces back to an Indo-European root reconstructed as *bʰleh₁-, which also has the modern English descendent bleat. You will notice that flebilis lost some bits in the passage: the -bilis became -ble, as it always did (like goats to cows – “billies” to “bull”), but it also lost the l after the f, just because. And then that vowel stuff happened.
That vowel stuff happened a lot in French. Latin e sounds sometimes stayed e but sometimes became oi, as in voir and noir and quite a few others. But that oi in turn sometimes kept going – and sometimes English took the word at the oi stage but French moved it on to ai. (The shift in pronunciation from /e/ by way of /oi/ and /we/ to /ɛ/ can be inferred by those who care enough about it.) For example, françois became français except in the name François; reconnoistre (from Latin recognoscere) became reconnoître and was taken by English as reconnoitre, but then moved on to reconnaître in French; connoisseur (a noun formed from connoistre, which is reconnoistre without the re) stayed that way in English but became connaisseur in French. And Latin flebilis became Old French fleible, which became feble and foible, and feble came into English and became feeble while foible came into English and became the noun we know and love, foible; meanwhile, in French it moved on to become modern faible, which has a much broader sense of ‘weak’ (including instances we would translate as low or minimal).
So there it is. More alacrity than lachrymose, more sweeping than weeping, as far as I’m concerned, but, then, I’m the sort of person who spends a Friday evening on this kind of thing.