You may want to check the spelling of entomology and etymology.
Etymology is the branch of language study that investigates the history and origins of words. As an example, the word etymology itself comes from two Greek words, etumon (~ 'the true thing') and logos (~ 'the study or science of'). This develops from the idea that the true meaning of a word is its original meaning - not an idea currently held by linguists, who view language as a constantly changing thing. Consequently it is now recognised that the meanings of words are constantly changing, and that their origin is not always the best guide to their current meaning. Nevertheless, some readers find etymology useful in suggesting the meaning of a word, explaining its spelling or giving mnemonic support. It is also interesting, at times, in illustrating cultural history as well as language itself.
The word 'etymon' - pronounced with the stress on the first syllable, IPA: /ˈɛt ɪ mɒ(or ə)n/ (the Greek plural - regular in that language - is etyma, /ˈɛt ɪ mə (or a)/, although etymons has been seen in English) - is currently used in academic circles to mean 'root', or 'earliest meaning'. In Ancient Greek ἔτυμον (etumon), the neuter of the adjective ἔτυμος‚ (etumos, true) was used in the same way to mean 'the true sense of a word according to its origin'.
You may like to follow AWE's English etymology course, or Outline History of the English language.