From Longman Business Dictionary
custodiancus·to·di·an /kʌˈstəʊdiən-ˈstoʊ-/ noun [countableC]1someone who is responsible for looking after something valuable for another person or for the publiccustodian ofAs the former custodian of Europe’s strongest currency, the deutsche mark, the Bundesbank effectively dictated monetary policy across the Continent.
2LAW in the US, someone who represents the interests of a child and is responsible for looking after their money and propertyThe custodian will manage the property if the gift giver dies before the child has reached the age of 21.