There are a lot of Latin words that begin with se-. It adds the notion of being "apart" or "separated":
The linked entry calls it an "inseparable prefix" meaning "aside / by itself." Wiktionary associates it with the reflexive pronoun se. There also seems to be a separate (apparently unrelated) meaning where se is a contraction of sine, e.g. securus = sine cura.
These options provoked some questions for me:
- If se- is related to the reflexive pronoun, how do we make sense of the "apart" meaning?
- If se- is a preposition, why does it only appear as a prefix? It reminds me of secus, but seems to have the opposite meaning.