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c.1600, "belonging to the earliest age," 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 is from a best-selling book of 1971.
primal pri·mal (prī'məl)
Being first in time; original.
Of first or central importance; primary.