Plural of castor; small swiveling wheels attached to furniture legs, or beaver-related items.
From French 'castor' (beaver), named because the wheels were originally made with beaver fur or the term was borrowed for wheeled furniture legs moving like a beaver's mobility.
Furniture wheels called 'castors' take their name from beavers because of the animal's legendary ability to move nimbly across terrain—medieval inventors apparently saw a connection between beaver agility and smooth-rolling wheels.
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