The word 'vocab' is a 20th-century English slang clipping of the noun 'vocabulary'. 'Vocabulary' itself entered English in the 16th century from Medieval Latin vocabularium, meaning a list of words, which derives from Latin vocabulum (a word, a name). Vocabulum comes from vocare (to call), tracing back to the Proto-Indo-European root wekw- (to speak). The modern truncation 'vocab' follows a common pattern in informal English where longer words, especially those used frequently in educational contexts, are shortened for convenience, retaining the core semantic association with words and language.

This word is a modern English truncation of "vocabulary". It is not formed from classical morphemes in its current state.