Amusingly strange, silly, or eccentric in a fun or harmless way that makes people laugh.
American slang from the 1950s, possibly derived from 'cuckoo' (which means crazy). The spelling with 'k' and double-o made it sound more whimsical and playful.
The 1960s TV show 'The Addams Family' perfectly captured what 'kooky' meant—Cousin Itt and the whole family were wonderfully bizarre but lovable, and the word became popular right around that era when quirky was becoming cool!
Complete word intelligence in one call. Free tier — 50 lookups/day.