I just ran across a French word I’d been unfamiliar with, cheptel ‘livestock’ (though technically ‘livestock’ is cheptel vif, cheptel mort being ‘farm equipment’). I immediately identified it as being from Latin capitalis, the adjective of caput ‘head,’ but how exactly was it derived? The che- clearly indicated a direct (“popular”) descendent, but the -p- was out of place and suggested a learned formation. Upon consulting my Nouveau dictionnaire étymologique du français by Jacqueline Picoche (Hachette, 1971), a very useful work, I discovered I was right on both counts; it was listed s.v. chef under “mots demi-savants”: “Cheptel XVIIe s. : réfection, par adjonction d’un p étym. de l’anc. fr. chetel (pop.) XIe s. : lat. capitale, adj. neutre substantivé, « le principal (des biens possédés) ».” So the -p- was added by savants who knew the Latin derivation.
I also used the Advanced Search interface of the online OED to see if it would turn up anything of interest, and it pointed me to the entry for another word hitherto unknown to me and quite interesting in its own right, steelbow (Sc. Law. Obs. exc. Hist.) “A quantity of farming stock, which a tenant received from his landlord on entering, and which he was bound to render up undiminished at the close of his tenancy.” (Here‘s the Dictionary of the Scots Language entry.) The OED etymology (unchanged since 1916) reads:
< steel n.1 + bow n.3
It corresponds to the French cheptel de fer (see Littré), lit. ‘iron farm-stock’, and to early modern German stählin vieh, eisern vieh (in German Law Latin pecora chalybea, ferrea), and obsolete Danish jernfæ. These terms denote the quantity of live stock which a farming tenant receives from his landlord on entering, under a contract to restore the same quantity and value at the end of his tenancy. This is precisely the sense of steelbow, exc. that the Scots term seems to have been extended to apply to dead as well as live stock. The French cheptel de fer is also used, like steelbow, for the species of tenure or contract under which cattle are so held by a tenant. In early modern German there were other legal terms containing the adjs. stählin ‘made of steel’, eisern ‘made of iron’, in the figurative sense ‘rigidly fixed in amount’: e.g. stähline gült, a fixed regular payment or income: stähline pfründe, a church living subject to no deductions. The figure of speech doubtless comes down from very early Germanic legal formulæ; but evidence is wanting. See Schilter Glossarium, s.v. Stal; also Grimm Deutsche Rechtsaltertümer (ed. 4, 1899) II. 131.
I should point out that the “bow n.3” refers to the original numeration; in the current online OED, the sense intended—”The stock of cattle on a farm, a herd” (from Old Norse bú farming, a farm, farm stock)—is bow n.4, so the link is misleading; I’ve e-mailed them to that effect.