Used informally to soften the harshness of 'die'. Not used in formal situations. Old Bob pegged out at 90, had a good innings.
Pro Tip 2/3
Humorous Undertone
Sometimes used humorously about ones' or others' potential death scenarios. If I eat another bite, I'll peg out!
Pro Tip 3/3
Avoid Formal Usage
Not appropriate in serious or formal contexts, such as funerals or official documents. The coroner's report would not state that the individual 'pegged out'.