deafyoudaoicibaDictYouDict[deaf 词源字典]
deaf: [OE] Ultimately, deaf and dumb come from the same source, and moreover they are related to a Greek word for ‘blind’. The common denominator ‘sensory or mental impairment’ goes back to an Indo-European base *dheubh-, which denoted ‘confusion, stupefaction, dizziness’. It produced Greek tuphlós ‘blind’; English dumb; and a prehistoric Germanic adjective *daubaz ‘dull, stupefied, slow’.

Many of the modern descendants of *daubaz retain this general sense – Danish doven means ‘lazy’ – but English has specialized it to ‘dull in hearing’. Duffer may ultimately be derived from Old Norse daufr ‘deaf’ in which the sense ‘dull, stupid’ is preserved.
=> duffer, dumb[deaf etymology, deaf origin, 英语词源]
deaf (adj.)youdaoicibaDictYouDict
Old English deaf "deaf," also "empty, barren," specialized from Proto-Germanic *daubaz (cognates: Old Saxon dof, Old Norse daufr, Old Frisian daf, Dutch doof "deaf," German taub, Gothic daufs "deaf, insensate"), from PIE dheubh-, which was used to form words meaning "confusion, stupefaction, dizziness" (cognates: Greek typhlos "blind," typhein "to make smoke;" Old English dumb "unable to speak;" Old High German tumb).

The word was pronounced to rhyme with reef until 18c. Deaf-mute is from 1837, after French sourd-muet. Deaf-mutes were sought after in 18c.-19c. Britain as fortune-tellers. Deaf as an adder (Old English) is from Psalms lviii:5.