“It is interesting to take up one or the other of the expressions which designate the guardian angel and which make it easier to understand his role. He is called ‘guardian’ (phylax) or ‘guard’ (phrouros). There are also the terms ‘protector’ (prostates) and ‘superintendent’ (epimeletes) and ‘overseer’ (ephoros). Another name is ‘assistant’ (boethos). Particularly interesting is the name ‘shepherd’ (poimen). His guardian angel appeared to Hermas in the form of a shepherd. Basil calls his ‘herdsman’ (nomeus). Eusebius gathers the different names together and says: ‘Fearing lest sinful mankind should be without government and without guidance, like herds of cattle, God gave them protectors and superintendents, the holy angels, in the form of captains and shepherds. His First-Born Son is set above all of these.’”
-Jean Danielou in The Angels and Their Mission According to the Fathers of the Church.