Collin is a spelling of Colin, which has two separate sources: in England it began as a medieval pet form of Nicholas, "victory of the people", while in Scotland and Ireland it comes from the Gaelic Cailean and means "young pup" or "whelp". The double-l spelling has been the more American of the two for decades. Collin was number 128 in 2000, its best year in this century, and has declined gradually since to number 493 in 2025.