idiotic (adj.)

1713, from idiot + -ic or from Late Latin idioticus "uneducated, ignorant," in classical Latin, "of an ordinary person," from Greek idiotikos "unprofessional, unskilled; not done by rules of art, unprofessional," from idiotes "unskilled person" (see idiot). Idiotical is from 1640s. Related: Idiotically.