The word 'whack' is first recorded in English in the early 18th century. It is believed to be an onomatopoeic formation, created to imitate the sharp, resonant sound of a solid blow. This sound symbolism directly links the word's form to its core meaning of a hard hit. Over time, its usage expanded metaphorically; in informal contexts, it came to denote one's allotted portion or share, perhaps from the idea of a fair division struck or "whacked" out.

The word 'whack' is considered a simplex word. It is likely of imitative origin, formed to mimic the sound of a sharp blow.