Byname
/ˈbaɪneɪm/
Definition 1 of 1
Pro Tip 1/3Informal Usage
Bynames are typically used in casual, informal contexts, not in formal situations like business meetings. 
My friends call me 'Sparky', a byname I got during a camping trip.
Pro Tip 2/3Expressing Personality
A byname often reflects a person's characteristics, behavior, or something notable they're known for. 
He's called 'Flash' because he runs so fast.
Pro Tip 3/3Endearment or Teasing
Bynames can be a sign of friendship or affection, but sometimes they can be used to tease. 
We all smiled when the coach called her 'Tiny' for her fearlessness despite her small size.