John Lockin’ it means in slang: If one makes it seem like his/her legs aren’t working. The person may lose control over their legs, and then collapse. These legs become dehydrated and must be carried around to regain their health. It was the first time this happened in LOST. John Locke, a TV star, lost his feeling in his legs and collapsed while walking. (in Slang Dictionary, added by Malapropism)