Two ideas raced together to make one character: 大, the wide-armed person you already met, now tilted forward mid-stride with arms pumping, planted above 止, a bare footprint. Swinging arms plus a moving foot — the scribes drew running before they ever drew a gentle stroll, and only later did 走 settle into its calmer, everyday sense of simply going somewhere on foot.
A piece of culture
Going through the back door Chinese has a vivid phrase for pulling strings instead of following the rules: 走后门 (zǒu hòumén), literally "to walk through the back door." While ordinary people queue at the front gate, someone with the right connections slips in around the side. The idiom is used today for everything from landing a hospital appointment to getting a job through a friend of a friend, and it always carries a note of gentle disapproval.
Use it in a real word
走人
zǒurén · zau2 jan4
to leave; to get going — a colloquial phrase; you already know 人