The oracle-bone drawing shows a footprint rising up out of a hollow in the ground: toes pointing away from the pit, the mark of an early dwelling dug low for warmth. To leave home, you first had to step up and out of it — and that single step became the character for "to exit" and "to go out".
A piece of culture
Choosing a lucky direction to step out Traditional Chinese almanacs (黄历) don't just list dates — they list which direction is lucky to walk out of your door that day, especially for the first outing (出行) after Lunar New Year. Even now, some families check the almanac before a long trip, a house move, or a wedding, choosing not just a lucky day but a lucky direction for that first step outside.
Use it in a real word
出门
chūmén · ceot1 mun4
to go out (the door); to leave home — literally "exit" + "door"; you already know 门