“etymology: The study of the historical relation between a word and the earlier from or forms from which it has, or has hypothetically, developed. Thus the etymology of sheep relates it, with German Schaf and others, to a reconstructed Common Germanic skoepa; that of street relates it, through Old English straet, to a borrowing into Germanic of Latin (via) strata ‘paved road.’
Loosely described as a study of the ‘origins of words’; but any form may have an earlier prehistory, over many thousands of years, of which we can know nothing.”
Excerpted from: Matthews, P.H., ed. The Oxford Concise Dictionary of Linguistics. New York: Oxford University Press, 2014.