Racial slur used by U.S. troops during the Philippine-American War of 1898–1902/1913. Derogatory. Equivalent to the racial epithet, "nigger", which was also used to refer to Filipinos.
Google "Goo Goo Philippines" and reference Wikipedia "Philippine-American War"
"No cruelty is too severe for these brainless monkeys, who can appreciate no honor, kindness, or justice… With an enemy like this to fight, it is not surprising that the boys should adapt ‘no quarter’ as a motto and fill the blacks with lead. Let's go Goo Goo hunting."