Theodore R. Rosche {letters, April 21} denies Justice Antonin Scalia's derivation of the word "cretin" from "Christian" and asserts that it ultimately refers to the island of Crete. However, the New Testament passage he cites (Titus 1:12) connects the inhabitants of Crete not with any lack of intelligence but with mendacity: "The Cretans are always liars, evil beasts, slow bellies." And indeed mendacity, not stupidity, was the general reputation of Cretans in antiquity. Thus, the Liddell-Scott Greek lexicon defines the ancient Greek verb kretizo as "to play the Cretan, i.e., lie."

"Cretin" is normally thought to come from the Swiss French dialectical term crestin, usually thought to be the local word for Christian. In standard French, the words are very close: cretin for "cretin," and chretien for "Christian." The derivation from "Christian" is not universally accepted. The article on "cretinism" in the 11th Edition of the Encyclopedia Brittanica prefers a derivation from creta "clay," because of the sallow complexions of cretins in the narrower sense -- i.e., sufferers from the thyroid deficiency of cretinism, which normally results from a lack of iodine in the diet and typically occurs in mountain valleys like those in the Swiss Alps.

But the derivation from "Christian" is normally accepted -- e.g., by the American Heritage Dictionary and by Webster's Word Histories. The Oxford English Dictionary not only accepts the derivation from "Christian" but documents it: The earliest instance of the word "cretin" that it gives, from 1779, refers to a species of idiots peculiar to the Swiss canton of Valais. DONALD F. McCABE Takoma Park