the.com/keyring

A small metal hoop whose job is to make losing many keys as easy as losing one.

means A ring or small chain that holds multiple keys together so they can be carried and used as a single unit.

from A plain compound of 'key' and 'ring,' describing exactly what it is — a ring for keys. Keys themselves trace back to Old English 'cæg,' of uncertain deeper origin, while 'ring' comes from Old English 'hring,' a very old Germanic word for a circular band. The device likely emerged once people carried enough keys (house, chest, cabinet) that a loose jangling handful became impractical — a humble, functional invention named with no fuss at all.

origin
split-ring design borrowed from book-ring binders
capacity myth
too many keys wears down ignition cylinders
psychology
decorative fobs exist mainly to aid frantic searching
etymology
ring once meant any circular binding object
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