olemus
sõltub kontekstist ja õigusruumist

Wiktionary:
1. a person entrusted with the custody or care of something or someone; a caretaker or keeper
After their parents' death, their aunt became the children's custodian.
The building's custodian could fix nearly anything. The place always looked great!

näiteid
custodian bank -- depoopank, hoiupank
custodian services -- väärtpaberite hoidmine
custodian bank account -- alaealisele vanemate avatud pangakonto

ISO 6707-4:
omandi või andmike valvaja ja kaitsja või hooldaja
= one who guards and protects or maintains property or records

ISO/IEC 27050:
isik või üksus, kelle omanduses, hoole või kontrolli all
on elektrooniliselt talletatav teave
= person or entity that has custody, control or possession of electronically stored information

vt ka
- andmekäitleja