One peculiarity of English phonetics is that weakly stressed vowels tend to be pronounced as a shwa. For example, the a in sofa, the e in modest, and the o in police are all pronounced as a shwa. Due to that leveling, a person hearing a shwa in a word may not know which corresponding written vowel to use in spelling the word—as we see in the common misspelling definately for the correct definitely.
I bring all this up because some months ago I discovered that Google gave me 264,000 hits for *antisematism and 90,000 more for *anti-sematism. The numbers were small when compared to the 25,000,000 for the correct antisemitism, but still large in absolute terms. In contrast, because of the distinctly pronounced vowels in Spanish, a search for *antisematismo produced only 32 hits on Google.
As for the origin of the correct antisemitismo/antisemitism, the anti- is the familiar prefix meaning ‘against’ and the main part of the word is a reference to the semitas/Semites. The Encyclopedia Britannica says this about the word Semite:
Person speaking one of a group of related languages, presumably derived from a common language, Semitic (see Semitic languages). The term came to include Arabs, Akkadians, Canaanites, some Ethiopians, and Aramaean tribes including Hebrews. Semitic tribes migrated from the Arabian Peninsula, beginning c. 2500 bc, to the Mediterranean coast, Mesopotamia, and the Nile River delta. In Phoenicia, they became seafarers. In Mesopotamia, they blended with the civilization of Sumer.
The word semita/Semite itself goes back to the Greek version of Shem, the Hebrew name of the son of Noah from whom the Semitic peoples are supposed to have descended. In the term antisemitismo/antisemitism, of course, the Semitic group almost always being referred to is the Jews, though I suppose someone who hates Arabs could also be called an anti-Semite.
© 2012 Steven Schwartzman