omicron

The story

1. Koine Greek · derived fromὂ μῑκρόν“little o”
2. Latin · borrowed fromomicron
3. English todayomicron

From Latin omicron, from Koine Greek ὂ μῑκρόν (ò mīkrón, “little o”), named in contrast with omega (“big o”). The uncommon form omicra is similarly borrowed from Latin and Greek. The use for designating stars in a constellation—typically in order of apparent brightness—began with Johann Bayer's 1603 Uranometria.