doaitni

According to Stüber, from to- +‎ ad- +‎ *tind (“bright”, an adjective only attested in later Irish).^[1]

do·aitni (verbal noun taitnem)

1. to shine
   • c. 700 Immram Brain, published in The Voyage of Bran son of Febal to the land of the living (1895, London: David Nutt), pp. 1-35, edited and with translations by Kuno Meyer and Alfred Nutt, stanza 3

     Fil inis i n-etarchéin imma·taitnet gabra réin, rith find fris tóibgel tondat, cetheóir cossa fos·longat.

     There is a distant island around which the horses of the sea [i.e. waves] glisten; a fair course against the white-swelling surge, four feet upholding it.

   • c. 700–800 Táin Bó Cúailnge, from the Yellow Book of Lecan, published in The Táin Bó Cúailnge from the Yellow Book of Lecan, with variant readings from the Lebor na hUidre (1912, Dublin: Hodges, Figgis, and Co.), edited by John Strachan and James George O'Keeffe, TBC-I 3125

     It é súile na caurad assa cennaib-sin do·raitniset frit amail óible[a] tened.

     [Fergus describing what Mac Roth saw] They were the eyes of the warriors that were flashing from their heads to you like sparks of fire.

2. to please
   • c. 850 Glosses on the Carlsruhe Beda, published in Thesaurus Palaeohibernicus (reprinted 1987, Dublin Institute for Advanced Studies), edited and with translations by Whitley Stokes and John Strachan, vol. II, pp. 10–30, Bcr. 44^b2

     do·n-aitni

     when it is pleasing

• In the Milan glosses, this verb is replaced by a simple deponent verb taitnigidir.

• Middle Irish: taitnid, taitnigid
  • Irish: taitin, taitnigh

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