Hip

As a noun, the hip is the joint where the top of your leg meets your body. As an adjective (informal), hip means fashionable, cool, or up-to-date.

The body-part sense comes from Old English “hype” or “hip,” related to Germanic words for the same joint. The slang sense “hip” meaning “in the know” appeared in American English in the early 1900s, possibly from African American vernacular, though its exact origin is debated.