What is the meaning of Custos?

A warden.

A monastic superior, who, under the general of his order, has the direction of all the religious houses of the same fraternity in a given district, called a custody of the order.

In older forms of musical notation, an indication, at the end of a line of music, of the first note of the next line.

A guard, protector, watchman

A guardian, tutor

A jailer

A keeper, custodian

plural of custo

Source: wiktionary.org