Why do only a few English demonyms indicate gender?

A friend recently pondered why Latino/Latina inflects according to gender. I suggested that it's because Latino is a loanword from a language with grammatical gender, but he found it odd that other demonyms don't inflect this way, and he wondered whether there was something etymologically or historically unique about the word. Wikipedia offers a long list of demonyms, and only Pinoy/Pinay and Canadien(ne) inflect like this.

I also noted that Englishman has a feminine ‑woman form, although the etymology here is different. Etymology Online attests that Englishman dates to Old English, whereas gendered Englishwoman is a newer form (c.1400). This inflection appears to have a different productive mechanism, one that mainly applies to places with significant Anglophone or Norse history: Englishman, Frenchman, Irishman, Dutchman, Scotsman, Chinaman, Welshman, Norseman (roughly in order of usage).

Is there any etymological rhyme or reason to this? Why do we inflect Latino and Canadien but not other words derived from non-Germanic languages like Spaniard? Why do we have Irishwomen but not Italianwomen (and only very rarely Spanishwomen)?

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Update: MετάEd answered this satisfactorily for the native demonyms ending in -man: In those cases, the gendered variants are largely the result of a semantic shift where Old English man “person” became Middle English man “male” and woman “female.” However, I'm still looking for an explanation of why English adopted the gender inflection of Latino, Filipino, and Pinoy, unlike most other demonyms. Is this perhaps because they are endonyms used by a significant number of bilingual English speakers?

Answer

Spanish has a fairly simple system of indicating gender agreement that is familiar to a great many English speakers (maybe most), which means English speakers are more likely to be aware of how to inflect Spanish adjectives for gender than adjectives from most other languages.

Even though French gender agreement is also relatively simple—mostly a matter of adding "e"—the resulting forms would often be homophonous if read using English conventions, which I think leads to more confusion. The French-derived words that are inflected in writing in English, such as né(e) and fiancé(e), are fairly often misspelled.

Additionally, the word "Latino/Latina" entered English relatively recently, so it's had less time to lose foreign affixes and become naturalized. The earliest citations for Spaniard in the Oxford English Dictionary are from around the fifteenth century, while the earliest for Latino is 1946.

The continued use of these terms by bilingual speakers, as you have mentioned, is also likely to play a role in the maintenance of the gender distinctions. Pinoy and Pinay in particular seem to me to be used most often by Filipinos or people of Filipino ancestry, rather than by other English speakers.