the.com/castor

means A small swiveling wheel fixed under furniture to let it roll — also the name of an oil pressed from a bean and one of the Gemini twins in the sky.

from From Latin 'castor,' meaning beaver, itself borrowed from Greek 'kastor.' Beavers produce a musky secretion called castoreum, once prized in medicine and perfume, which pulled the word into use for oils and ointments generally — castor oil actually comes from the castor bean plant, not beavers at all, a naming coincidence that confuses people to this day. The furniture wheel sense likely arose separately, from the verb 'to cast' (as in cast down or throw), describing something set rolling. Castor the star and mythological twin comes from a different Greek source entirely — a hero's name, unrelated to the beaver — making this word a case of three or four distinct histories wearing the same coat by accident.