A hog is a large male pig. I don''t know if you've ever seen pigs on a farm when they are being fed, but they are very greedy. They push and shove each other and steal each others food. The phrase "to hog" probably originated on a farm. If a parent buys one bike for two children to share, but one of the children always takes it for himself, then he is "hogging the bike". In other words, he is being compared to a large male pig who is greedy. Just remember that the phrase "to hog" isn't very insulting. It's usually said in a playful way. Children will say it to each other in an angry way, but it's not a harsh insult for an adult.
"Don't hog the remote" - This is a command you can use when the other person is always holding on to the television remote and choosing the channels.
"Don't hog the bathroom" - This is a command you can use when someone is always in the bathroom and you want to get in there so you can use it.
"Roadhog" - This is someone who drives in a fast and dangerous way which causes everyone else to brake, or swerve out of the way, or avoid his crazy driving.
"To hog glory" - This is when a team of people did the work, but one person is trying to take credit for it.