Depiction of a man carrying an axe on over his shoulders. The right side of the form was later phoneticized into 可. The current meaning "what" is a phonetic loan.

Evolution

Oracle script

(~1250-1000 BC)

Bronze script

Early Western Zhou (~1000 BC)

Seal script

Shuowen (~100 AD)

Clerical script

Eastern Han dynasty (25-220 AD)

Regular script

Modern

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