pager friend; beeper buddy
Slang from the 1990s pager (beeper) era; refers to a person one communicates with primarily via pager, often without meeting in person. Now largely historical.
In the 90s, many young people exchanged messages daily with their pager friends via pocket bells.
Compound of ベル (from 'bell', referring to a pager/beeper) and 友 (friend). Coined during the pager boom in 1990s Japan.