et·y·mol·o·gy 
(ĕt′ə-mŏlə-jē)
(ĕt′ə-mŏlə-jē)n. pl. et·y·mol·o·gies
1. The origin and historical development of a linguistic form as shown by determining its basic elements, earliest known use, and changes in form and meaning, tracing its transmission from one language to another, identifying its cognates in other languages, and reconstructing its ancestral form where possible.
2. The branch of linguistics that deals with etymologies.
[Middle English etimologie, from Old French ethimologie, from Medieval Latin ethimologia, from Latin etymologia, from Greek etumologiā : etumon, true sense of a word; see ETYMON + -logiā, -logy.]