Language Of Confusion: Prefixes, Part I

I’ve actually already done some of these, so this is a little bit of a redux. But there are a lot of prefixes I’ve never looked at, so let’s get to it!
 
Ex-
Ex usually means out of or from, but can also mean upwards, completely, deprive of, former, or without. No, nothing contradictory there. It’s from the classical Latin ex, which means from, and that can be traced to the Proto Indo European eghs, out. If it’s out in some way, it’s ex-.
 
Dis-
Dis- (or dif-, or just di- in front of some consonants) tends to mean one of three things, lack of/not, opposite of, and apart or away. It’s from the Old French des- and classical Latin dis-, which also means apart. It goes all the way back to the Proto Indo European dis-, which is just apart or asunder.
 
De-
De- generally means down, from, or concerning, although it does occasionally act as an undoing of something, like in defrost, a holdover from how it’s used in Latin. In Latin, de means about, and it’s from the Proto Indo European de-, which also happens to be related to the origin word for to. Basically, everyone used de- in their own way, and English has traces of all of those.

Sub-
Sub- generally means under, behind, or from below, which makes sense, since sub means under in Latin. It shows up in more words than you might think, as the b tends to be dropped, or sometimes it’s replaced with an r. It’s from the Proto Indo European (s)up-, which is from the root upo, under or up from under.
 
Com-
Com- is another prefix that can be different depending on which letter it’s in front of. In some places it’s co-, in some it’s con-, and sometimes it’s col-, cor-, or cog-. But they all come from the same place and mean with or together. They’re from the classical Latin cum, with, which is from the Proto Indo European kom-, beside, near, or with. In spite of not being able to make up its mind what it wants for its third letter, it’s pretty straightforward.
 
Un-
Un- is actually weird because there are actually two versions of it that seem related, but aren’t. The first one is negation—like unheard of or uncalled for. It’s from the Old English un-, from the Proto Germanic un-, from the Proto Indo European n-, meaning not. The other un- prefix means reversal or removal—like undoing or unbuttoning. While these two un-s seem very much related, they’re not. This un- comes from the Old English on- (to be fair, that could have also been spelled un-), and that’s from the Proto Germanic andi-, and that certainly won’t be confused with un-. That’s from the Proto Indo European anti, facing opposite, before, or against. And if you’re thinking that sounds a lot like anti-, that’s because that’s where it’s from, too.
 
Sources
Online Etymology Dictionary
Google Translate
Omniglot
University of Texas at Austin Linguistic Research Center
University of Texas at San Antonio’s page on Proto Indo European language
Tony Jebson’s page on the Origins of Old English