Nowadays if someone is called a “gentleman,, it mostly means they they’re polite. You’d think, since the word “gentle” is part of “gentleman,” that such a fellow would be particularly unlikely to rap you over the head with his walking-stick, or challenge you to a duel of swordplay. But the meaning of “gentle” has changed quite a lot since it was adopted into English from the Old French “gentil.” “Gentle” originally meant the same as “noble”, back when that had to do entirely with your parents and nothing to do with your motives or sensibilities.
In fact, being a “gentleman,” back a thousand years or so, was almost exactly the opposite of what we might expect. A “gentleman” was a social rank (a very formal one, not “social” as in “social media”), and with it came the right to carry a sword. Being “gentle” back then was the opposite of being “simple” — which meant that you were born to a low rank.
Social rankings and the family you were born into were considered of utmost importance back in the days before anybody was supposed to be able to prosper on their own merits. If you carried a sword openly (not that hiding it would be easy), that was an indication of your rank, because the “simple folk” weren’t allowed to have weapons. (I wonder why…). You might be called a “squire,” which was a social rank in itself, and is the source of the “esquire” you still see appended to the names of attorneys.
“Squire” is also borrowed from Old French, in which it was “esquier.” Later on it came to be used to mean a knight’s assistant, but originally it was simply a rank all on its own. None of these ranks had anything to do with your behavior, of course. The whole notion of “nobility” meaning something other than your birth rank — that is, the idea that the people born to the right families were in some way superior not just in inherited rank but in character, principles, or ideals — that’s just the result of an effective public relations campaign a few centuries back.
One result of that PR campaign was a curious word that isn’t used very much any more, but really deserves to be resurrected: “squiriferous.” It simply meant “acting like a squire” — and because of its interesting timing, coming after people had been convinced that words like “noble” and “gentle” had more to do with character than genealogy, it referred to the kind of “squire” that was more like a knight’s assistant than simply a male member of a privileged family. You’ll find “squiriferous” in Charlotte Turner Smith’s novel Marchmont, published in 1796: “Squiriferous Parsons, young men in orders, who shoot, hunt, etc.” Although Marchmont isn’t very widely known now, it’s an interesting example of the early cracks in the notion of “nobility” as a matter of superior character. Its major theme is about how “the law” (and remember, attorneys to this day use the appellation “esquire”) can be used by people born to privilege but lacking anything resembling “noble character” to ruin the lives of innocent people, particularly if they’re not privileged. After all, who do you think wrote those laws?
Charlotte Smith, by the way, is a pretty interesting person in her own right. She published ten novels, but considered herself primarily a poet. She was married at the age of 15, evidently because her father needed money, but later left her husband and supported herself and her twelve (!) children through writing. She also campaigned, in the late 1700s, for women’s rights and legal protections. As far as I know she never made her feelings known in this area, but I’m guessing she probably wouldn’t have wanted to be described as “squiriferous.”