Plural of hairball; clumps of hair that form in an animal's stomach, especially in cats, or tangled balls of loose hair.
From 'hair' (Old English 'hǽr') combined with 'ball' (from Old Norse 'bollr'). The compound word emerged naturally as people observed this common phenomenon in pets.
Hairballs are actually a medical concern vets take seriously, but the word itself became more famous through jokes about cats—yet they're equally a human problem in bathtubs and drains everywhere.
Complete word intelligence in one call. Free tier — 50 lookups/day.