The verb iniungere (a compound of in- and iungere) literally means "to join, fasten, attach". However, an Etymonline entry also gives it a figurative meaning "to inflict, to attack, impose". How was the meaning generalized from the neutral literal meaning to the somewhat hostile figurative one?
This r/classics post answers my question.
IonCharge. 19 days ago
I would hazard a guess and say it was a result of the farming connotation with iugum "yoke" (hence iniungere = to join two bulls together to draw a plough) which had already extended its semantic field to include marriage and slavery. Ultimately the iugum represented some element of mastery and domination, whether over farming animals, women, slaves, etc.
To join together > to yoke > to enslave > to impose
If this is the case, the semantic shift began around 7-8c BCE. Within a few hundred years of Rome’s founding the Romans would “subjugate” those defeated in battle, if not outright slaughtering them. It’s been a while so my dates may be off, but it was before or during the Hellenistic period when this shift happened.
This could easily be proto-Italic, though I'm sure some Latin speakers were savvy enough to know that iugum and iungere were cognates. I'm going to need a source on that dating.
breadyly. 19 days ago
idk if this will answer your question, but when joining two things together, it can be either passive or forced, hence the more hostile meaning
Peteat6. 19 days ago
I don’t know, but if there’s a fight about it, I want to join in. Haha! See what I did there? Of course you did.