Castor
/ˈkæstər/proper noun
One of the twin Dioscuri, brother of Polydeuces, and the name of the second-brightest star in the constellation Gemini, after Pollux.
The Greek roots
Literally: “Castor”
The story of the word
Castor was the mortal twin, the horseman, and when he was killed his immortal brother asked to share his own immortality, so the pair alternate between heaven and the underworld. Sailors prayed to them, and the electrical glow on a ship's mast in a storm is still called St Elmo's fire after a Christianised version of the same protective pair. The identical Greek word κάστωρ also means beaver, source of the medicinal secretion castoreum, and whether the god's name and the animal's are truly one word is not settled. Castor oil, pressed from a bean and not from any animal, seems to have taken the name when it replaced castoreum in the medicine chest.
- How it travelled
- Ancient Greek → Latin → English
Same family
In a sentence
Castor sits above Pollux in the winter sky, and the fainter of the two is the brighter star.