Vocabulary (n.) - Let's build a big one.
A list of words with definitions, and explanations.
Also all of the words and individual or group understands when heard and knows how to use.
History & Etymology
Vocabulary comes into English from Medieval Latin, the language spoken by the educated and literate, for a vast period of time throughout Europe. In Latin it was vocabularium, which referred to “a list of words” originally. Which came from the Latin vocabulum meaning “word, name, or noun” that word came from vocare which meant “a name, or to call(as in to get someone's attentions). Vox was latin for voice, you probably recognize it from “Vox Populi,” the voice of the people. This word vox is the origin of vocabulary in Latin.
The first known use of the word vocabulary in the modern sense was in the 1750s. Prior to that the word solely referred to a listing of words with definitions and explanations, similar to a modern dictionary.