deuceyoudaoicibaDictYouDict[deuce 词源字典]
deuce: [15] The underlying meaning of deuce emerges most clearly in its application to playing cards and dice: the number two. It comes from Old French deus ‘two’, which goes back to duōs, the accusative case of Latin duo ‘two’ (English two comes ultimately from the same source). Its use in tennis comes from the French phrase à deux, literally ‘at two’, which signifies that a player must score two successive points to win a game. It is generally thought that the mild oath deuce came from duus, the Low German descendant of Latin duōs, which gamblers supposedly cried out in disgust when they threw the lowest score, a two.
[deuce etymology, deuce origin, 英语词源]
dyad (n.)youdaoicibaDictYouDict
1670s, from Latin dyad-, stem of dyas, from Greek dyas "the number two, a group of two," from duo "two" (see two). Specific sense in chemistry ("a bivalent element") is by 1865; also used in biology, poetics, mathematics. Related: Dyadic.
eye (n.)youdaoicibaDictYouDict
c. 1200, from Old English ege (Mercian), eage (West Saxon) "eye; region around the eye; apperture, hole," from Proto-Germanic *augon (cognates: Old Saxon aga, Old Frisian age, Old Norse auga, Swedish öga, Danish øie, Middle Dutch oghe, Dutch oog, Old High German ouga, German Auge, Gothic augo "eye").

Apparently the Germanic form evolved irregularly from PIE *okw- "to see" (cognates: Sanskrit akshi "the eye; the number two," Greek opsis "a sight," Old Church Slavonic oko, Lithuanian akis, Latin oculus, Greek okkos, Tocharian ak, ek, Armenian akn).
HAMLET: My father -- methinks I see my father.
HORATIO: Where, my lord?
HAMLET: In my mind's eye, Horatio.
Until late 14c. the English plural was in -an, hence modern dialectal plural een, ene. Of potatoes from 1670s. Of peacock feathers from late 14c. As a loop used with a hook in fastening (clothes, etc.) from 1590s. The eye of a needle was in Old English. As "the center of revolution" of anything from 1760. Nautical in the wind's eye "in the direction of the wind" is from 1560s.

To see eye to eye is from Isa. lii:8. Eye contact attested from 1953. To have (or keep) an eye on "keep under supervision" is attested from early 15c. To have eyes for "be interested in or attracted to" is from 1736; make eyes at in the romance sense is from 1837; gleam in (someone's) eye (n.) "barely formed idea" is from 1959. Eye-biter was an old name for "a sort of witch who bewitches with the eyes."
number (n.)youdaoicibaDictYouDict
c. 1300, "sum, aggregate of a collection," from Anglo-French noumbre, Old French nombre and directly from Latin numerus "a number, quantity," from PIE root *nem- "to divide, distribute, allot" (related to Greek nemein "to deal out;" see nemesis). Meaning "symbol or figure of arithmetic value" is from late 14c. Meaning "single (numbered) issue of a magazine" is from 1795. Meaning "dialing combination to reach a particular telephone receiver" is from 1879; hence wrong number (1886). The modern meaning "musical selection" (1885) is from vaudeville theater programs, where acts were marked by a number. Earlier numbers meant "Harmony; proportion calculated by number," and "Verses, poetry" [Johnson].

Number one "oneself" is from 1704 (mock-Italian form numero uno attested from 1973); the biblical Book of Numbers (c. 1400, Latin Numeri, Greek Arithmoi) so called because it begins with a census of the Israelites. Slang number one and number two for "urination" and "defecation" attested from 1902. Number cruncher is 1966, of machines; 1971, of persons. To get or have (someone's) number "have someone figured out" is attested from 1853. The numbers "illegal lottery" is from 1897, American English.