Etymology
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aid (v.)

"to assist, help," c. 1400, aiden, from Old French aidier "help, assist" (Modern French aider), from Latin adiutare, frequentative of adiuvare (past participle adiutus) "to give help to," from ad "to" (see ad-) + iuvare "to help, assist, give strength, support, sustain," which is from a PIE source perhaps related to the root of iuvenis "young person" (see young (adj.)). Related: Aided; aiding.

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deaf (adj.)

Old English deaf "lacking the sense of hearing," also "empty, barren," from Proto-Germanic *daubaz (source also of 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" (source also of 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. Meaning "refusing to listen or hear" is from c. 1200. As a noun, "deaf persons," from c. 1200. 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 (see adder).

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aid (n.)

early 15c., aide, "war-time tax," also "help, support, assistance," from Old French aide, earlier aiudha "aid, help, assistance," from Late Latin adiuta, noun use of fem. of adiutus, past participle of Latin adiuvare "to give help to," from ad "to" (see ad-) + iuvare "to help, give strength, support, sustain," which is from a PIE source perhaps related to the root of iuvenis "young person" (see young (adj.)).

The meaning "thing by which assistance is given" is recorded from 1590s; the sense of "person who assists, helper" is from 1560s. The meaning "material help given by one country to another" is from 1940.

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Band-Aid (n.)

trademark name (Johnson & Johnson) for a stick-on gauze pad or strip, by 1922. See band (n.1) + aid (n.). The British equivalent was Elastoplast. Figurative sense of "temporary or makeshift solution to a problem, pallative" (often lower case, sometimes bandaid) is attested by 1968; as an adjective in this sense, by 1970.

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surd (adj.)

1550s, "irrational" (of numbers), from Latin surdus "deaf, unheard, silent, dull; willfully deaf, inattentive," possibly related to susurrus "a muttering, whispering" (see susurration). The mathematical sense is from the use of Latin surdus to translate Arabic (jadhr) asamm "deaf (root)," itself apparently a loan-translation of Greek alogos, literally "speechless, without reason" (Euclid book x, Def.). In French, sourd remains the principal word for "deaf." As a noun from 1540s. Related: Surdity.

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deafen (v.)

1590s, "to make deaf," from deaf + -en (1). The earlier verb was simply deaf (mid-15c.). For "to become deaf, to grow deaf," Old English had adeafian (intransitive), which survived into Middle English as deave but then took on a transitive sense from mid-14c. and sank from use except in dialects (where it mostly has transitive and figurative senses), leaving English without an intransitive verb here. Related: Deafened.

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deafness (n.)

"incapacity of distinguishing or perceiving sounds," late 14c., defnesse, from deaf + -ness.

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lip-read (v.)

1880, back-formation from lip-reading, which is attested from 1852 in writings on educating deaf-mutes; from lip (n.) + reading.

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sign language (n.)

"system of communication using gestures," especially for communication with and among the deaf, by 1847; see sign (n.). Earlier hand-language (1670s).

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leg up (n.)

"an aid, a boost," 1837, from leg (n.) + up (adv.).

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