c. 1600, "belonging to the earliest age or stage," from Medieval Latin primalis "primary," from Latin primus "first" (see prime (adj.)). Psychological sense, in reference to Freud's theory of behaviors springing from the earliest stage of emotional development, is attested from 1918. Primal scream in psychology is from a best-selling book of 1971 (Arthur Janov, "The Primal Scream. Primal Therapy: The Cure for Neurosis"). Related: Primality.