Especially now with the movie "le petit lieutenant", I'm puzzled about the origin of this word. "lieu" means place and "tenant" is keeping or holding. So, the literal meaning of the word is one who is a keeping or holding a place. Was the lieutenant the one who was left with terroritory that had just been won or taken? Or is my analysis of the word wrong.

Just wondering.

That's what the OED online said. And Wikipedia, but they go into a bit more detail...

the lieutenant is exactly as in wikipedia says.
the title given to the person who keeps the property for the rightful owners.
now it just has a military title of course.

Thanks for the hyperlink to the OED online. That's invaluable. I don't trust Wikipedia, so I would never go there for information, but thanks for confirming what I figured out.