vocabulary (n.) Look up vocabulary at Dictionary.com
1530s, "list of words with explanations," from Medieval Latin vocabularium "a list of words," from Latin vocabulum "word, name, noun," from vocare "to name, call," related to vox "voice," from PIE root *wekw- "give vocal utterance, speak" (see voice (n.)). Meaning "range of words in the language of a person or group" is first attested 1753.