deac

• deëc

From Proto-Celtic *dekam-kʷe (literally “and ten”), with loss of the first k by dissimilation.^[1]

deäc

1. -teen

When modifying a noun to indicate an amount between 11 and 19, deac follows the noun while its accompanying numeral simultaneously precedes the noun.

• c. 800–825, Diarmait, Milan Glosses on the Psalms, published in Thesaurus Palaeohibernicus (reprinted 1987, Dublin Institute for Advanced Studies), edited and with translations by Whitley Stokes and John Strachan, vol. I, pp. 7–483, Ml. 16^c10

  cóic bliadni deäc ― fifteen years (literally, “five years -teen”)

• Middle Irish: déc
  • Irish: déag
  • Scottish Gaelic: deug
  • Manx: jeig

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