c.1375, from Scottish, "heathen, pagan," and having that sense first in Eng., from Gk.
ta ethne, used in Septuagint translation to render Heb.
goyim, pl. of
goy "nation," especially of non-Israelites, hence "Gentile nation."
Ta ethne is from Gk.
ethnos "band of people living together, nation, people," prop. “people of one's own kind,” from PIE
*swedh-no-, suffixed form of base
*s(w)e- (see
idiom). Sense of "peculiar to a race or nation" is 1851, return to the word's original meaning; that of "different cultural groups" is 1935; and that of "racial, cultural or national minority group" is Amer.Eng. 1945.
Ethnicity is from 1953;
ethnic cleansing is from 1991.
[eth-nik] 
nɪk