late 14c., "being or pertaining to the source or beginning," from Late Latin primordialis "first of all, original," from Latin primordium "a beginning, the beginning, origin, commencement," from primus "first" (see prime (adj.)) + stem of ordiri "to begin" (see order (n.)). The sense of "first in order, earliest, existing from the beginning" is from 1785. Related: Primordially. Primordial soup as the name for the conditions believed to have been present on Earth circa 4.0 billion years ago, and from which life began, in J.B.S. Haldane's theory, is by 1934.