Greaser

“Greaser” is an epithet for a Mexican that was used in the 1840s, during the Mexican-American War. The derisive term still has some currency today.
   
   
(Historical Dictionary of American Slang, A-G)
greaser n.
a Mexican (hence) a Hispanic person of any nationality; (occ.) any person of southern European birth or ancestry.—used contemptuously.
1836 in G.A. McCall Letters (Apr. 23) 298: The pervading sentiment among the defeated an disorganized “Greasers” was, “sauve qui peut.”
1846 in Ill. State Hist. Soc. Jrnal. (Summer 1953) 166: They would (the greasers) raid and massacre all th Yankees.
1847 McClellan Mexican War Diary 69: The “Greasers” had it all in their own way.
   
15 October 1846, Defiance (OH) Democrat, pg. 2:
He promises all the “greasers” of Mexico the sacking of Matamoras, should he be victorious, of which he seems positive.