I always thought it was the most ridiculous name for them to pick for him (even considering the other ridiculous names in Star Wars - Biggs Darklighter, anyone?)
anything with -kin on the end denotes "sweet little thing" to me. Bunnykins, Kittykins, etc
Anakin the most puke-making name ever for a hero. Finding out Darth Vader's real name was Anakin is a bit like finding out that Count Dracula's real name is Nikki-Joe.