early 15c., "third of the lesser canonical hours," from Latin sexta (hora), fem. of sextus, ordinal of sex (see six).
Entries linking to sext
late 14c., "males or females collectively," from Latin sexus "a sex, state of being either male or female, gender," of uncertain origin. "Commonly taken with seco as division or 'half' of the race" [Tucker], which would connect it to secare "to divide or cut" (see section (n.)).
Secus seems the more original formation, but it is strange that the older texts only know sexus. The modern meaning of sectiō 'division' suggests that sec/xus might derive from secāre 'to sever', but the morphology remains unclear: does sexus go back to an s-present *sek-s- 'to cut up', or was it derived from a form *sek-s- of the putative s-stem underlying secus? [Michiel de Vaan, "Etymological Dictionary of Latin and the other Italic Languages," Leiden, 2008]
Meaning "quality of being male or female" first recorded 1520s. Meaning "sexual intercourse" is attested by 1906; the meaning "genitalia" is attested by 1938. Sex appeal is attested by 1904.
For the raw sex appeal of the burlesque "shows" there is no defense, either. These "shows" should be under official supervision, at the least, and boys beneath the age of eighteen forbidden, perhaps, to attend their performance, just as we forbid the sale of liquors to minors. [Walter Prichard Eaton, "At the New Theatre and Others: The American Stage, Its Problems and Performances," Boston, 1910]
Sex drive is by 1918; sex object by 1901; sex symbol by 1871 in anthropology; the first person to whom the term was applied seems to have been Marilyn Monroe (1959). Sex therapist is from 1974.
"1 more than five, twice three; the number which is one more than five; a symbol representing this number;" Old English siex, six, sex, from Proto-Germanic *seks (source also of Old Saxon and Danish seks, Old Norse, Swedish, and Old Frisian sex, Middle Dutch sesse, Dutch zes, Old High German sehs, German sechs, Gothic saihs), from PIE *s(w)eks (source also of Sanskrit sas, Avestan kshvash, Persian shash, Greek hex, Latin sex, Old Church Slavonic sesti, Polish sześć, Russian shesti, Lithuanian šeši, Old Irish se, Welsh chwech).
Six-shooter, usually a revolver with six chambers, is first attested 1844; six-pack of beverage containers is from 1952, of abdominal muscles by 1995. Six of one and half-a-dozen of the other "little difference" is recorded from 1833. Six-figure in reference to hundreds of thousands (of dollars, etc.) is from 1840. Six feet under "dead" is from 1942.
Phrase at sixes and sevens originally was "hazarding all one's chances," first in Chaucer, perhaps from dicing (the original form was on six and seven); it could be a corruption of at cinque and sice "exposed to great risk" (1530s), literally "at five and six," using the French names (which were common in Middle English) for the highest numbers on the dice. Meaning "at odds, in disagreement or confusion" is from 1785, perhaps via a notion of "left unsettled."