quaternion

The story

1. Late Latin · derived fromquaterniō
2. Middle English · inherited fromquaterniǒun
3. English todayquaternion

From Middle English quaterniǒun, from Late Latin quaterniō, from quaternī (“four each”) + -iō, from quater (“four times”). Doublet of kern. The mathematics sense was coined by Irish mathematician and astronomer William Rowan Hamilton in 1843.