A foot 夂 coming down toward an opening 口 — someone arriving at a dwelling. The original sense was to arrive, preserved in 客 (guest, a visitor under a roof). Borrowed for its sound, it settled into the distributive meaning it has now: taken one at a time, each separately.
各 is everywhere in written and spoken Chinese: 各种 (all kinds), 各位 (everyone, addressing a room politely), 各自 (each on their own). 各有各的好 — each has its own merits — is the diplomatic way to end an argument about which thing is better.
A foot arriving at a door — everyone turning up one at a time, EACH on their own.
各 originally meant 'to arrive'. That sense survives in 客 (guest) — the same arriving foot, now under a roof.