Origin of the Term "Sidekick"

Sidekick is criminal slang, but did not originally mean an accoplice or partner. The word comes from the old fashioned name for the hip pocket in a man's trousers. Pick pockets used to name the various pockets they would try to steal from. So the inside breast was called the "well", the back pocket was called the "kick", and so on. But the hardest pocket to pick was the "sidekick" (the hip pocket), and therefore people who wanted to keep their wallets safe would put them in there. With time the term came to mean anything that's dependable and kept close at all times, and now means a partner or best mate.