Don't bug out! Entomology is the study of insects, but etymology is the study of words. They sound similar and both end in -logy, which means "the study of," but don't mix them up unless you like completely confusing people.
Entomology comes from the French entomologie and the New Latin entomologia. These come from the Greek éntomon, for insect, and logia, for study. Entomology, then, is the study of insects:
From the department of entomology you expect to learn something about the troublesome insects, which are so universal an annoyance. (A.W. Latham)
Entomology: that branch of Zoology that deals with insects and, specifically, the Hexapods. (John B. Smith)
The etymology of the word etymology is that it comes from the Old French ethimologie and the Latin etymologia. Both come from the Greek etymologia, from etymon, for "true sense," and logos, word. Today's etymology is the study of a word's history:
Dictionaries take decades to compile, while slang terms come in and out of fashion faster than you can say etymology. (Time)
In fact, Metcalf devotes a whole chapter to the various false etymologies of OK, including several you may have heard. (The Globe and Mail)
Thinking about the etymology of these words made me think about exactly why we, as designers, were originally inspired by these ideas. (Co. Design)
Remember, entomology is the study of insects, like ants. If you're talking about words and where they came from, use etymology.