The History of Herstory
Robin Morgan coined the neologism in 1970. She was well aware of the etymology of history. As she recalled in her book, The Word of a Woman (emphasis added)
[The essay] “Goodbye to All That” was my contribution to the first issue [Of Rat magazine upon its takeover by radical feminists in January 1970]. Beneath the byline, I identified myself as a member of WITCH—in this case, the flexible acronym stood for “Women Inspired to Commit Herstory.” (This was the debut of the word “herstory.” I intended it as a consciousness-raiser, not as an etymological claim.)
She also spelled out the word herstory, as part of the name W.I.T.C.H., on page 551 of her 1970 anthology, Sisterhood is Powerful.
In modern usage, the word has come to mean writing about history from a feminist perspective, rather than making it. (Wikipedia claims that “femistry” and “galgebra” are similar coinages, but in fact these appear to have been invented sarcastically by a right-wing pundit, Christina Hoff Sommers, in 2014, and I could find no examples of any feminists using them.)
Few if any influential feminists have ever said that history is a sexist word, although many anti-feminists appear to believe that they do. The 1988 edition of the Handbook of Non-Sexist Writing, for example, uses the word “history” throughout and pauses to sigh at “the belabored form of ridicule that we must find alternatives for every word containing” a syllable such as man.
The Afro-futurist musician Sun Ra made the same pun in 1980 (“History is only his story. You haven’t heard my story yet.”) also fully aware that this is not where the word comes from.
I have, however, personally been forced to sit through a college lecture by a woman who actually believed and taught the urban legend his+story. Despite her claim to diversity being that she was Latina, she also told the joke his+panic (and misattributed it to the Reagan administration, being unaware that the Nixon administration first added it to the 1970 Census more than a decade earlier) and also fell for per+son. (I was sorely tempted to ask if she was familiar with the Spanish word una persona.) So, a few ignoramuses like that do exist; in my life, I have met a total of one.
The Etymology of History
If we were to take the word absolutely literally according to its etymology, it would imply that “history” is written by an istor, or “wise man.”
With regard to the fact that historia is grammatically feminine, theories about the Indo-European three-gender system include one that the gender that became “feminine” originally developed from a suffix for mass nouns, or that it originally primarily denoted abstract nouns, or that it started as a way to distinguish which of two subjects in a sentence someone was referring to, and only later came to include most words for women. English developed natural gender in the early modern period.
The Etymology of His
Since no one has gone into this yet, his comes from a Saxon root is, cognate with German es, and meant either his or its until the 1600s. There was a brief period of time when hisis was to his as hers is to her, but this failed to catch on. Its was still new enough when the King James translation of the Bible was written that the translators did not consider it sufficiently formal, so they avoided both his and its for neuter possessives whenever possible, and used thereof instead. This is how they came up with, “Sufficient unto the day is the evil thereof.”