We speak English. And if you know anything about English you know that it is a language that appropriates words from other languages.
Another thing you should know is that what we call English is to a great extent a amalgimation of the Old English sopoke before the Norman conquest and more modern English spoken in the ensuing centuries.
The Normans ended up being the ruling class of England and they kept, at least to some extent, the language of Normandy. This brought about a division in language between the rulers and the ruled.
It also meant that for many things, animals for instance, there were two or more "English" names. Hogs & Swine for example. Lots of other examples out there if you think about it.
Could well be that in one instance the word from one segment of society prevailed in the modern world while in another situation things worked out differently.
Is any of this making sense............?
Isn't to me either..............but I think we're on the right track here. See below......
[Middle English, from Old French foun, faon, feon, young animal, from Vulgar Latin *fētō, *fētōn-, from Latin fētus, offspring; see dhē(i)- in Indo-European roots.]
Origin:
bef. 900; ME; OE cealf, calf; c. OS kalf, ON kalfr, OHG kalb