1670s, "pertaining to electors," in reference to Germany, from elector + -al (1). In general sense from 1790. Related: Electorally. The U.S. electoral college so called from 1808 (the term was used earlier in reference to Germany).
"one who elects or has the right of choice," mid-15c., from Latin elector "chooser, selecter," agent noun from past-participle stem of eligere "to pick out, choose" (see election).