kolegio

Here is a false seam that is true one layer down, which is the most confusing kind. Kolegio and kolego, a colleague, look related, and in Latin they genuinely are: collegium is precisely a body of collegae, of partners holding office together. So the learner's instinct is correct about the history and wrong about the language in front of them.

Wrong, because Esperanto has no such build. There is no suffix -i- meaning a collection of things, and the suffix that does that job is -ar-. A body of colleagues in Esperanto is a kolegaro, and it is a perfectly good word meaning the staff or the professional body you belong to. Kolegio is not built from kolego at all: it is a separate international root borrowed whole, and the fact that Latin had already done the composition is a gift the borrowing carries in rather than a rule you can run. The inspiri page has the same shape of story, where the Latin in- plus spirare is real and the Esperanto word is nevertheless one piece.

Then there is what the word actually means, which is not one thing. In Esperanto kolegio covers two senses that English also runs together. First, an institution of education above school and often below or inside a university, so li studas en kolegio is unremarkable. Second, a formal body of people holding the same office: la kardinala kolegio is the College of Cardinals, and kolegio de advokatoj is a bar association. The second sense is the older one and is the one that keeps the Latin meaning alive.

Set it against the neighbours. A lernejo is a school, built from lerni plus the place suffix; a universitato is a university; gimnazio is a grammar school in the continental sense; and kolegio sits between them, vaguely, in exactly the way the English word does.