Etymology is the study of root words, or the history of words. Etymologists discover how words are formed and what their meaning is and how that meaning has changed over time.
cachalot
cachepot
cachet
cacidrosis
cacoepy
cachinnate
cacodoxy
cacolet
cacogen
cacoethes
caballine
caboose
cabochon
caboched
cable
cabas
cabrie
cabriole
cacography
cacogenics
caconym
cadastre
cacotopia
cacuminal
caddis
cacology
caducary
cadrans
cabotage
cabré
cabriolet
cachaemic
cacaesthesia
cacodemomania
cachexic