Fulvous has never been a common word. You are most likely to encounter it in texts from the 19th century—unless, that is, you care about ducks. In that case, you might know about a kind of whistling-duck called the fulvous tree duck, which is a brownish duck with long legs and a long neck and an unusual world distribution. It lives in isolated populations in North America, South America, India, and Africa—remarkably without geographic variation. But back to fulvous: it shares a meaning with its direct ancestor, the Latin word fulvus, and fulvus itself is believed to possibly share an ancestor with flavus, Latin for "yellow."