Fair meant beautiful before it meant light-complected, not the other way around. Fair derives from Old English faeger (beautiful, lovely, pleasant), which came from the Germanic and Norse fagar and fagr for beautiful. Until the 1550s, fair was used to describe a beautiful or attractive person with no regard to the color spectrum, and indeed with not much regard to sex. "The men of this province are of a fair and comely personage, but somewhat pale," wrote the narrator of The Travels of Sir John Mandeville (circa 1357-1371).
This changed with the Elizabethan era, and with that great language alchemist, Shakespeare. The bulk of his sonnets were addressed to whom his scholars call the "Fair Youth"—and his uses of fair in these sonnets sticks with the original meaning. But the youth in question is described as having a "gold complexion"—after all, we're comparing him to a summer's day—and during this time the meaning of fair broadened to include skin tone. Just in time, too; with the arrival of Africans in England in 1551, Britons suddenly needed a term to distinguish their pale-skinned beauties from the new arrivals. (Certainly it's no coincidence that this era saw an uptick with the usage of fair to mean "morally good." That usage dates back to the 12th century, but the late 16th century introduced the phrases fair play and fair and square, setting the race status quo early on. It worked on the other side too: The 1580s saw the first use of black to mean "dark purposes," alongside its prexisting adjective use to describe dark-skinned people.)
This is also the same period during which the term "the fair sex" originated as a designation for women of a certain class. Erasmus in 1533 queried "the Artifices us'd by such of the Fair Sex as aim more at the Purses than at the Hearts of their Admirers," already using the term ironically even though it had only just then been introduced. And even jumping the pond, fair soon became a catch-all reference to American women—well, the white ones, at least—as beautiful, light-skinned, and morally virtuous. "Strategic deployment and ordinary usage of the term 'fair sex' produced white women as a special category: a racialized sex group that lost consciousness of itself as bounded by race and class, retaining the memory of its identity as one based on gender alone," write Pauline E. Schloesser in The Fair Sex: White Women and Racial Patriarchy in the Early American Republic. "Once the discourse was deployed, one understood universals like 'females,' 'ladies,' and 'the sex' to mean white and middle-class without having to make these specific references." Fair, in America, became a way of determining how western European one was. An 1850 genealogical compendium from Harvard delineated pale skin from fair skin, the former indicating an Eastern European heritage instead of the British-Germanic pink undertones of fair skin. Fair skin was also thin and soft, as opposed to the thick, hard, dry—that is, working-class—complexion of pale-skinned folk.
But all this is in the past, right? The olden days? Have you ever heard someone describe a woman as fair without referring to her complexion? Even in today's most popular use of fair outside of skin tone, My Fair Lady, we understand the term to be quaint, archaic, charming, much like the class system it mocks. (Plus, it's unlikely that Lerner and Loewe would have come across this title organically; My Fair Lady took its title from Pygmalion: Fair Eliza, one of the considered subtitles for the 1912 play that inspired the latter production. And even that was borrowed from Robert Burns's 1791 poem "Thou Fair Eliza.")
It's not in the past, though. I'd argue fair-as-beautiful continues to be relevant, even as that direct use of fair has ceased. (It's worth noting that the first-listed definition in Merriam-Webster is still "pleasing to the eye or mind," however.) Its history is encoded in its complexion reference: Fair is a less racially charged way of saying white. I've argued before that the skin-whitening creams found throughout Asia reflect a desire for class status, not whiteness per se; just as having a tan in America signifies you have the time and resources to take long beach vacations from our indoor jobs, having pale skin in Asia signifies that you've risen above menial outdoor labor. But the use of that particular word—fair—crops up time and time again with these products. Fair and White, Fair and Lovely, Fair and Flawless, Fair Lady (one of the few products recalled) are but a few of the products that use the word. So even without evoking Caucasian skin, fair conjures a particular kind of woman: not only one who is whiter-skinned than most Asians, but one who is delicate, refined, and working indoors (or not at all). Fair is aspirational.
There's another archaic use of fair that I'm seeing cropping up more and more. While most of Shakespeare's sonnets were written for the Fair Youth, a handful were penned for the Dark Lady. These were passionate, sexual sonnets, in contrast to the tenderness of the poems for the Fair Youth. We've continued this dichotomy, hypersexualizing today's "dark ladies" even if American beauty standards are finally becoming more inclusive (well, somewhat). We've got the spicy Latina; sultry, exotic women of the Middle East (surely they belly dance!); sexy squaws; and, of course, the ubiquitous bootylicious black women that populate hip-hop videos. It's not an issue of dark-skinned women being seen as less beautiful; it's an issue of them being seen as beautiful in a particular way. A way, not incidentally, that precludes them from being a part of "the fair sex," which preserves the term's original connotations of class and delicacy. Dare I go for the obvious here? It's not fair.