The quality of being catchy or memorable, especially in a way that stays in your mind easily.
From 'catchy' (from 'catch' meaning to seize or grab) + '-ness' suffix forming abstract nouns. The sense evolved from literally 'catching' attention to describing anything memorable or appealing.
Catchiness is why pop songs get stuck in your head—advertisers and musicians deliberately engineer it by repeating melodic or lyrical hooks. Your brain's pattern-recognition system literally can't let go of certain sequences, which is why 'Baby Shark' haunted an entire generation.
Complete word intelligence in one call. Free tier — 50 lookups/day.