Oíngus

Old Irish

From oín (“one”), from Proto-Celtic *oinos, from Proto-Indo-European *óynos (“single, one”). The etymology of the second element is disputed; most likely it is gus (“strength, vigour”), from Proto-Celtic *gustus, or it may be from Proto-Celtic *gus- (“choose”), from Proto-Indo-European *ǵews-.

Oíngus m (genitive Oíngusa)

(Irish mythology) The Gaelic god of love, youth, and poetic inspiration, son of the Dagdae and Boann of the Túatha Dé Danann.
a male given name, equivalent to English Angus

Masculine u-stem
	Singular	Dual	Plural
Nominative	Oíngus	—	—
Vocative	Oíngus	—	—
Accusative	Oíngus^N	—	—
Genitive	Oínguso^H, Oíngusa^H	—	—
Dative	Oíngus^L	—	—
Initial mutations of a following adjective: ^H = triggers aspiration ^L = triggers lenition ^N = triggers nasalization

Middle Irish: Oéngus, Aengus
- Irish: Aonghas
- Manx: Anghus
- Scottish Gaelic: Aonghas, Aonghus
  - → English: Angus

Old Irish mutation
Radical	Lenition	Nasalization
Oíngus (pronounced with /h/ in h-prothesis environments)	unchanged	nOíngus
Note: Some of these forms may be hypothetical. Not every possible mutated form of every word actually occurs.

Gregory Toner, Sharon Arbuthnot, Máire Ní Mhaonaigh, Marie-Luise Theuerkauf, Dagmar Wodtko, editors (2019), “Oengus”, in eDIL: Electronic Dictionary of the Irish Language