Latin caput supplied Late Latin capitaneus, meaning chief. The word passed through Anglo-French capitain and Middle English capitane.
Capit- is the Latin stem used in formation, not an additional historical word to rank.
Sources
- Merriam-Webster: captain
Latin caput precedes Late Latin capitaneus, Anglo-French capitain, Middle English capitane and modern captain.
- Anglo-Norman Dictionary · capitain
Meanings of the older forms on the word path.
- Online Etymology Dictionary · captain
Meanings of the older forms on the word path.