|Nome = Ernest David
|Cognome = Klein
|Sesso = M
|LuogoNascita = Satu Mare
|GiornoMeseNascita = 26 luglio
|AnnoNascita = 1899
|LuogoMorte = Ottawa
|GiornoMeseMorte = 4 febbraio
|AnnoMorte = 1983
|Attività = filologo
|Attività2 = lessicografo
|Nazionalità = rumeno
|NazionalitàNaturalizzato = canadese
Nato in una famiglia [[ebraismo|ebraica]], all'età di nove anni era già in grado di recitare a memoria l'intero ''[[Salmi|Libro dei Salmi]]''. A 15 anni imparò l'[[lingua inglese|inglese]] come autodidatta usando testi in inglese. Aveva una grande capacità di apprendere nuove lingue.
In an interview by The Canadian Jewish News (August 1, 1975), Klein recalls traveling from his birthplace Satu Mare, Romania to Austria, a little uneasy at the prospect of studying in a foreign country where he did not know the language. Klein taught himself German during the few days journey, and by the end of the year he was the best pupil in his class. Later, over the years Klein acquired knowledge and knew over 40 languages.
Klein studied languages, philology and exact philosophy at the University of Budapest and the University of Vienna; he received his Doctorate of Philosophy from the latter in 1925. Fifty years later, in 1975 at a ceremony held in Canada by the Austrian Consulate, Klein was awarded the "Golden Ph.D." on his promotion to Doctorate of Philosophy by the University of Vienna.
He was the rabbi of the Nové Zámky community, Czechoslovakia, from 1938 Érsekújvár, Hungary, now Slovak Republic, from 1929 to 1944. That year, he was deported to Auschwitz and later to the Dachau concentration camp, where he was liberated. After the war he served as rabbi in Satu Mare. After emigrating to France, he was a rabbi of the synagogue on Rue de Montevideo in Paris (1950–1951) and in 1952 he emigrated to Canada, where he held the post of Rabbi of Congregation Beth Yitshak in Toronto until his death.
He is the author of A Comprehensive Etymological Dictionary of the English Language (1966–1967).
He is also the author of A Comprehensive Etymological Dictionary of the Hebrew Language for Readers of English (1987), an English-language etymological dictionary of Hebrew to which he devoted the last ten years of his life.
In 1978, he was made an Officer of the Order of Canada.