alternative (adj.)
1580s, "offering one or the other of two," from Medieval Latin alternativus, from Latin alternatus, past participle of alternare (see alternate (v.)). Meaning "purporting to be a superior choice to what is in general use" was current by 1970 (earliest reference is to the media). Alternative energy is from 1975. Related: Alternatively.
alternative (n.)
1620s, in rhetoric, from Medieval Latin alternativus (see alternative (adj.)). Of courses of action, from 1814. Of objects, etc., "the other of two which may be chosen," by 1838.