I did, in fact, look to the OED (yay public library database access!) and they have quotations for "fair sex," "fairer sex," and "sterner sex.' Note the (also ...) for each, as it shows the objectionable baggage carried by the terms.
Originally Posted by JunkMonkey
a. the fair (also gentle, soft, weak, etc.) sex : the female sex, women. Similarly †the devout sex , †the woman sex , the second sex .
In more recent use often ironical or humorous (as also in senses Phrases 1b and Phrases 1c).
1536 P. Melancthon Confessyon of Fayth of Germaynes f. 24, This happenyd also..in Monasteries of women..not withstonding that the weake sexe or kynde ought more to haue ben spared.
[1583 P. Stubbes Anat. Abuses sig. Eviiv, The magnificency & liberalitie of that gentle sex.]
1652 R. Brome Joviall Crew iii. sig. H4, I am bound by a strong vow to kisse all of the woman sex I meet this morning.
c1660 J. Evelyn Diary anno 1644 (1955) II. 246 The Pillar..at which the devout sex are always rubbing their Chaplets.
1688–9 J. Evelyn Mem. (1857) III. 294 Lovers and courters of the fair sex.
1694 N. H. Ladies Dict. Ded. sig. A2, To the Ladies, Gentlewomen, and Others, of the Fair-Sex, the Author Humbly Dedicates this following Work.
1702 C. Beaumont J. Beaumont's Psyche (new ed.) xiv. l. 213 The softer sex, attending Him And His still-growing woes with tenderer eyes.
1716 Pope tr. Homer Iliad II. v. 435 The King insults the Goddess as she flies..Go, let thy own soft Sex employ thy Care.
1732 G. Berkeley Alciphron I. ii. xxiv. 142 The fair Sex have now nothing to do but dress and paint.
1801 Port Folio (Philadelphia) 23 May 166/3, I prefer the favours of the fair sex to the company of the soakers, and so there is an end to all drinking.
1821 Byron Don Juan: Canto IV cviii. 125 Benign ceruleans of the second sex! Who advertise new poems by your looks.
1836 W. Irving Widow's Ordeal in Magnolia for 1837 257 It is somewhat remarkable that..the gentler sex should have been most frequently the subjects of these rude trials.
1838 E. Bulwer-Lytton Alice II. iv. vi. 14 In addition to those qualities which please the softer sex, Legard was a good whist-player.
1896 J. K. Bangs House-boat on Styx vii. 86 But go along and have your ladies' day here, and never mind my reasons for preferring my own society to that of the fair sex.
1928 D. K. Parker tr. Schopenhauer: Selections 443 Women..form the sexus sequior—the second sex.
1953 H. M. Parshley tr. S. de Beauvoir (title) The second sex.
1974 J. Mitchell Psychoanal. & Feminism ii. ii. 306 Woman is the archetype of the oppressed consciousness: the second sex.
1996 L. Lowndes How to make Anyone fall in Love with You xxxvi. 217 Another gentle habit of the gentle sex that, unfortunately, drives men stark raving berserk.
2008 N.Y. Rev. Bks. 26 June 44/3 The translation is sometimes old-fashioned (who now describes women as ‘the fair sex’?).
And on the other side, OED also has quotations for option c.
b. With comparative adjectives: the fairer (also gentler, softer, weaker, etc.) sex .
1578 T. Churchyard Disc. Queenes Entertainm. sig. F. iij, The weaker sexe, in beautie doth excell.
1618 R. Brathwait Good Wife sig. B6, in P. Hannay Happy Husband (1619) , He should dispence with lighter faults, not vex Himselfe for trifles, shee's the weaker sex.
1665 R. Boyle Occas. Refl. v. ix. sig. Ll8v, Persons of the fairer Sex.
1702 C. Beaumont J. Beaumont's Psyche (new ed.) xiv. l. 213 The softer sex, attending Him And his still-growing woes.
1753 W. Hogarth Anal. Beauty x. 65 An elegant degree of plumpness peculiar to the skin of the softer sex.
1786 Adventures George Maitland II. v. 116 Her voice was shrill, but melodious, she spoke with a readiness and facility upon most subjects, and possessed an understanding not very common in the softer sex.
1860 ‘G. Eliot’ Mill on Floss I. i. vi. 76 It was rather hard on Maggie that Tom always absconded,..but the weaker sex are acknowledged to be serious impedimenta in cases of flight.
1894 C. D. Tyler in Geogr. Jrnl. 3 479 They are beardless, and usually wear a shock of unkempt hair, which is somewhat finer in the gentler sex.
1961 ‘F. O'Brien’ Hard Life v. 42 Decent people should look after women—isn't that right? The weaker sex.
1997 Daily Express 19 Feb. 23/1 Far from being the gentler sex, they [sc. women as bosses] are more likely to behave like dictators.
2005 Good Weekend (Austral.) 8 Jan. 8/2 A distinctive Japanese style of manga cartoon for the fairer sex.
c. the sterner (also†better, †rougher, stronger) sex : the male sex, men. Now rare.
1608 Bp. J. King Serm. St. Maries Oxf. 27 Nature hath more enabled the stronger sexe to vndergoe this burthen.
1665 T. Herbert Some Years Trav. (new ed.) 22 Whiles the better sex seek prey abroad, the women (therein like themselves) keep home and spin.
1702 G. Miège New State Eng. (ed. 4) ii. 82 A Queen, whose incomparable Wisdom will ever be admired by future Ages, as..a Pattern to Princes of the better Sex.
1724 Love upon Tick 18 Whatever Influence, Age, or Infirmities, may have on one, and that the rougher sex, yet the Impressions made on the other are so deep [etc.].
1782 W. Cowper Conversation in Poems 254 Divest the rougher sex of female airs.
1819 J. Foster Contrib. Eclectic Rev. (1844) I. 508 It was not..thought too much for persons of the stronger sex, to go and return many miles on foot.
1822 Scott Fortunes of Nigel I. Introd. Ep. p. ix, I abide by the general opinion, that he is of the rougher sex.
1849 C. Brontë Shirley III. xiv. 312 ‘Mama’ is rather a misanthropist, is she not? Not the best opinion of the sterner sex?
1861 Southern Literary Messenger May 397/2 It is perhaps from utter despair..that so many of the better sex have..perpetrated of late years so many extravagancies in that region [sc. the north].
1915 New Fun 12 June 11/2 Now, through not taking a man's part, we have turned them into a weaker sex, and it is we girl-boys who are the stronger sex.
1927 Bright Ideas for Entertaining (rev. ed.) 233 If women are to do men's work in the world, the occupations of the sterner sex must change also and become those formerly handled by women.
1997 Harper's Mag. June 29/2 If women are to do men's work in the world, the occupations of the sterner sex must change also and become those formerly handled by women.
2005 Statesman (India) (Nexis) 5 Sept., King Parikshit and maybe King Janaka restore our faith in the sterner sex somewhat, but..the draw of the novel lies in the strength of its women.