Deprive means to keep from having. If your little brother gets loud and hyper every time he eats sweets, your parents might deprive him of sugary cereal and candy.
Deprive can also mean to take away something that someone already had, or feels they deserve to have, like basic human rights. "A crowd gathered to protest the man's imprisonment for a crime he did not commit; they didn't want to allow the government to deprive him of his freedom." The word comes from the Latin, de", which means "entirely," and privare, which means "release from." Put together, they mean to "entirely release from." In this case, the imprisoned man's freedom is being "entirely released," or taken away, and he'll no longer have it.