g-dangle
A nickname you give to someone you respect and know well. It’s not just a title, it’s a promise, and it usually involves some pretty wild behavior and a lot of swearing.
'You’re my g-dangle. I’ll back you up in a fight and take the hit for you.'
'She’s my g-dangle. We’ve been cussing each other out since we were kids.'
'He called me his g-dangle and said I was ‘the only one who could handle his mess.’'