I suppose it all originates from our repressed Victorian sexualities, from back when everybody thought they were the only ones to suffer the secret shame of being an actual wanker.
Most children these days learn the word "wanker" long before they learn its literal meaning.
Oh gosh! How did you know?
He lost both of his hands in a childhood kiting accident.
What a wanker!
2) Basically the same as 1) above but a narcissist who, having had their pride bruised by someone, decides it is a mature and reasonable course of action to define aforementioned person on a definition website with details of said infidelity plus various fabrications about their sexual and/or culinary desires. Someone who publicly blames their own inadequacies on someone else.