北 (běi) 'north' is a pictograph of two people standing back to back. Its original sense was 'back' or 'to turn the back', and because traditional Chinese houses faced south, the back of the building faced north, so the character came to mean the north direction. The original 'back' sense was then written with a new character 背 (bèi), which adds the flesh radical.

Origin

pictograph

Root

two people standing back to back