Kooky

wiktionary

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kook +‎  -y. 

etymonline

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kooky (adj.)

1959, American English, originally teenager or beatnik slang, possibly a shortening of cuckoo.

Using the newest show-business jargon, Tammy [Grimes] admits, "I look kooky," meaning cuckoo. [Life magazine, Jan. 5, 1959]

Related: Kookily; kookiness.