As we are now going into the realms of horses, I see from
@Olaszinhok that he quotes Frankish
marh for 'horse'.
Here's a thought. The old word for horse in Cymraeg/Welsh is
march /marX/, which is on a par with the current Breton word,
marc'h and Irish
marc. (See also, Old English,
mearh). It will also be recalled that Esyllt's (> Isolde, Iseult) husband and Tristan's uncle, who is also King of Cornwall, in
Tristan ac Esyllt is Marc/Mark.
In Modern Welsh,
march is more 'stallion' or 'war-horse' or 'steed' and its rider,
marchog i.e. 'knight'. We use
ceffyl (<
caballus) for 'horse', today.
Just another aside. seeing the Slavs use
'kov-' for to forge (post 7), the Welsh and Cornish word for a blacksmith is
gof, the etymology of which GPC cites as being purely Celtic. (It is one of only two words to have the plural ending
-aint). Blacksmiths were highly valued in Celtic myth.
This gives the 'English' surnames,
Gough and
Goff (and possibly then by extension
van Gough - but not the 'van' bit!)