Is there a verb for making a person chaste, e.g. putting a chastity device on them (or oneself)? I don’t mean “neuter” or “geld”; they imply surgery. And I know “chastise” isn’t right.
Howsabout “chasten”? See definitions 2 and 3.
Reminds me of a joke my dad used to make: “Mary is beautiful and chaste… by every guy in town.”
Chasten is definitely apropos. However, I’ve seen “chastise” more commonly used in exactly the context you describe, even though it’s considered an archaic usage meaning chasten according to Merriam-Webster. It seems to be making something of a comeback. What makes you say it’s not right?
I don’t like “chastise” because it usually means “reprimand,” which brings in different connotations than simply installing a chastity device. So I guess “chasten” is closer to what I’m looking for.
Chasten is the same as chastise in my book. The first definition in the link Heart of Dorkness provided above says chasten means “To correct by punishment or reproof; take to task.”
I don’t believe there is a verb with the specific meaning, “to keep [someone] chaste, as by fitting [them] with a chastity belt,” though definition 1 of chasten suggests uit can be used with that connotation.
You don’t need a special word for keeping someone chaste. You can just say “keep chaste”. That combination of words is usually used reflexively, meaning to remain chaste, but once you throw in a different agent and maybe mention a belt or something, then the reader will know what you mean. It’s not pedant-proof, but then what is?
it’s reassuring that it does not happen often enough to warrant a verb, like say throwing someone out a window.
I take it you haven’t been to Prague lately? 
Sometimes it only takes two instances to make a coinage stick. Ain’t language a funny old thing?
yeah, especially if you know there’s a cushion below. that’s just horse shit.
How about chaperone?
The OED lists “chastify” as an obsolete word with the meaning “to make celibate.” Maybe you can get the ball rolling on bringing it back into current usage.