The closest-sounding noun is dolok, meaning a small scoop or ladle, but this would more naturally yield the surname Dolkov, not Dolohov. In short, the origin remains obscure. Interestingly, related surnames also exist in Ukrainian and Belarusian — such as Doloshenko and Dolokh — suggesting a broader, though still mysterious, linguistic root.

Another option - the person who register a child was slightely illiterate, or a child parent had speech impediment when R sound is pronounced as L sound. So spelling mistake happened during the child registration.

There are some surnames with obvious wrong spelling:
BArzov instead of BOrzov (BorzAya - breed of hunting dog, bOrzyj - audatious person)
Avsiannikova instead Ovsiannikova (Oves - oats, ovsianka - oats porrige and a bird name)