nathardha
Definitions (by source)
adj. serpent-like; natharrda 2669.
Duanaire Mhéig Uidhir: The poembook of Cú Chonnacht Mág Uidhir, Lord of Fermanagh 1566-1589. Editor: David Greene. Translator: David Greene.
venomous, hence 'valorous'. niata nathardha, 2710; naitheardha, 1330.
Poems on the O'Reillys. Editor: James Carney.