arcuirethar

From ar- +‎ ·cuirethar. However, the related noun airchor is more often attested to mean a literal throwing sense instead of the extension sense of the verb.

ar·cuirethar

1. to extend
   • c. 845, St Gall Glosses on Priscian, published in Thesaurus Palaeohibernicus (reprinted 1975, Dublin Institute for Advanced Studies), edited and with translations by Whitley Stokes and John Strachan, vol. II, pp. 49–224, Sg. 6^b17

     .i. ar ní biat i n-anmanaib Laitindib ⁊ ní·erchuiretar lín liter Laitinde iarum.

     i.e. since [Y and Z] are not in Latin [words], and so they do not increase the number of Latin letters.

• airchor

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