`Luck'. This word is unusually interesting. It is
attested in early texts as meaning `omen', and the great Basque
linguist Michelena reconstructs the original sense as simply `bird'.
Centuries ago it was a common practice to try to foretell the future
by studying the flight of birds, and the Basque word for `bird' came
to have the sense of `omen'. It is the palatalized form of this word, (t)xori, which is today the universal Basque
word for `bird'.
Source: Some Basque Words