Castor Oil Has Nothing to Do With Beavers, and Also Does
Castor names a beaver, a small wheel and an oil. The oil's name came through a mix-up with a beaver secretion.
Castor is the Latin name for a beaver, and by extension the substance the animal produces. The oil is a case of mistaken identity: castor oil comes from a plant, but it was named because it replaced *castoreum*, a beaver secretion used in medicine. The wheel is a different word again, from *cast* meaning to turn.
- A small swivelling wheel. *Chair castors.*
- A plant oil. *A dose of castor oil.*
- A beaver, or its secretion. *Castoreum.*
- A container for sugar or salt. *A castor of sugar.*
Word forms
| Form | Word | Example |
|---|---|---|
| Noun | castor | A broken castor. |
| Plural | castors | Four castors. |
| Variant | caster | Caster sugar. |
| Related | castoreum | Medicinal castoreum. |
| Related | Castor | The star Castor. |
How it is used in a sentence
- The chair rolls on castors.Furniture.
- Caster sugar is finer than granulated.Named for the shaker it was poured from.
- Castor oil comes from a plant.Not from beavers.
The several castors
- Castor wheel — from *cast*, to turn or throw
- Castor oil — from the *Ricinus* plant
- Castoreum — a beaver secretion once used in medicine and perfume
- Caster sugar — fine sugar for sprinkling from a shaker
- Castor — one of the twins in the constellation Gemini
The wheel comes from *cast*, from Old Norse *kasta*, to throw. The oil and the animal come from Latin *castor*, from Greek *kastor*, a beaver.
Castor or caster?
Both spellings appear for the wheel. Caster is standard for the fine sugar and for a person who casts.
Does castor oil come from beavers?
No. It is pressed from the seeds of the castor oil plant. The name came from the beaver product it replaced in medicine.