thrilling, quavering; cf. Early Irish trílech, song, Old Irish trírech, song of birds. Cf. English trill, Italian trillare, Sp. trinar: an initiative word, English thrill is from the root tre, ter ( See tora), "piercing", which may also be the ultimate origin of the Gaelic words.
Etymological dictionary of the Gaelic language.
Alexander Gairm Publications.
1982.