In Latin, the word vice (two syllables) meant “alternate, in place of,” and, although it had the standing of a noun, there arose the practice in later Latin, and particularly in medieval Latin, of using it chiefly as one element of a compound noun.
A number of these compounds were taken into the various other Romance languages, and they are found in French chiefly with the spelling vis- or vi-.
So the Old French word for that member of the lower nobility who was an alternate count became visconte or viconte (modern French, vicomte), from the medieval Latin vicecomes.
On being taken into English, the spelling of the first part retained the French form, whereas the spelling of the second part was altered to the English form, to give us the half-French, half-English term viscount.
