laid-back

The term 'laid-back' originates from mid-20th century American English, specifically from the slang of jazz musicians. It is a figurative extension of the literal posture of being physically reclined or relaxed. The verb 'lay' (to put down) combines with 'back' to evoke an image of someone who has figuratively laid their concerns aside and leaned back from the stresses of life. This vivid imagery successfully transitioned from niche musical jargon into common parlance to describe a calm, unhurried, and easygoing temperament.

This is a compound adjective formed from the past participle 'laid' (from the verb 'lay') and the adverb 'back'. It functions as a single lexical unit.