The pamphlet was a hoax, concocted by Democrats, to discredit the Republicans by imputing to them what were then radical views that offended against the attitudes of the vast majority of whites, including those who opposed slavery.
There was already much opposition to the war effort.
Portuguese also uses miscigenação, derived from the same Latin root as the English word.
It purported to advocate the intermarriage of whites and blacks until they were indistinguishably mixed, as a desirable goal, and further asserted that this was the goal of the Republican Party.
Borrowing Boulainvilliers' discourse on the "Nordic race" as being the French aristocracy that invaded the plebeian "Gauls", he showed his contempt for the lowest social class, the Third Estate, calling it "this new people born of slaves ... Miscegenation comes from the Latin miscere, "to mix" and genus, "kind". The reference to genus was made to emphasize the supposedly distinct biological differences between whites and non-whites, though all humans belong to the same genus, Homo, and the same species, Homo sapiens.
The word was coined in an anonymous propaganda pamphlet published in New York City in December 1863, during the American Civil War.
In Spanish, Portuguese, and French, the words used to describe the mixing of races are mestizaje, mestiçagem and métissage.
These words, much older than the term miscegenation, are derived from the Late Latin mixticius for "mixed", which is also the root of the Spanish word mestizo.