spurious (adj.)

1590s, of persons, "born out of wedlock, bastard," from Latin spurius "illegitimate, false" (source also of Italian spurio, Spanish espurio), from spurius (n.) "illegitimate child," probably from Etruscan spural "public."

The sense of "having an irregular origin, not properly constituted" is from c. 1600; that of "false, sham, not what it pretends or appears to be" is from 1610s; specifically of writing, etc., "not proceeding from the source pretended," 1620s. Related: Spuriously; spuriousness; spuriosity.