caster / castor [ˈkæstɜr]
caster – n. – 1. one who makes moulds or forms; 2. a small swivelled wheel; 3. a small container with holes in the top for sprinkling the contents (sugar caster)
castor – n. – 1. a pungent, bitter-tasting, reddish brown substance obtained from the perineal sacs of the beaver, formerly used in medicine and perfumes; 2. castor oil – (a) an oil from seeds of a plant Ricinus communis; (b) this plant