The term refers to being controled by your significant other. It was created upon the idea of being caught in gun fire and not being able to escape it. It can also be used as being 'lenged'. The term was created by Gooneytoon to refer to a certain someone. Other simalar terms include 'being on lock', 'Your Girlfreind/Boyfriend wears the trousers' or plainly being 'whipped'.
"That boy is firing leng" (That boy is whipped)
"That girl has her boyfreind on leng." (His girlfriend wears the trousers.)
"Blud, you are lenged." (Friend, you are whipped)