What does the suf mean in suffix?

The "suf" in "suffix" comes from the Latin word "suffixum", which means "added on" or "attached".

Think of it like this:

* Suffix is a word part that is added to the end of a word to change its meaning.

* "Suf" (from "suffixum") implies addition or attachment.

So, "suf" in "suffix" signifies the addition of a word part to the end of a word.