One branch of the Rosario family is well-known as the Familian Ngånga'.
Ngånga' means "duck," as in the animal.
But I have heard of some of the Santos family, originating in Piti, also being called the Familian Ngånga', and I cannot find any connection between them and the Rosarios.
There may be no connection, as it is entirely possible that two unconnected families share the same nickname. One example of this is the Pepero nickname, which is used by some of the Dueñas family on Guam, but by some of the Sablan family in Saipan.