an honorific used in front of the names of outstanding personages

Examples from the Philippine Revolution (late 19th century):

Gat Jose Rizal
Gat Andres Bonifacio
Gat Apolinario Mabini


There are Filipino surnames still in use that bear traces of this word from ancient times:

Gatdula, Gatbonton, Gatsalian, Gatmaitan

A famous Filipino patriot who has a Gat- in his full name is Marcelo Hilario del Pilar y Gatmaitan (1850-1896), known popularly as Marcelo H. Del Pilar. This suggests that his mother's family was of noble origin.