mid-15c., "standing by itself," from Old French substantif, from Late Latin substantivus "of substance or being, self-existent," from Latin substantia "being, essence, material" (see substance). The grammatical term (late 14c.) was introduced by the French to denote the noun in contradistinction to the adjective, from Latin nomen substantivum "name or word of substance." Related: Substantival; substantively.
in grammatical use, late 14c., short for noun substantive, from Late Latin substantivium, neuter of substantivus "of substance or being" (see substantive (adj.)). Latin nomen substantivum was "name or word of substance."