Celtic (adj.) Look up Celtic at Dictionary.com
also Keltic, 1650s, of archaeology or history, from French Celtique or Latin Celticus "pertaining to the Celts" (see Celt). In reference to languages, from 1707; of other qualities, 19c. The Boston basketball team was founded 1946. Celtic twilight is from Yeats's name for his collection of adapted Irish folk tales (1893).