The term is a modern English compound, systematically constructed from fundamental linguistic elements to describe a familial timescale. The numeral "three" has an ancient, stable lineage from Proto-Indo-European, denoting a specific quantity. It is prefixed to the root "gener," derived from the Latin genus, which carries the core concept of birth, descent, and family line originating from the PIE root for begetting. The suffix "-ation" solidifies the combination into an abstract noun. Thus, the literal "three-births" or "three-origins" logically evolves into the contemporary sociological concept encompassing grandparents, parents, and children as a single relational unit.

Structure: three (number) + gener (produce) + ation (noun suffix) - three: From Old English þrīe, þrēo, from Proto-Germanic þrīz, from Proto-Indo-European tréyes. Functions as a numerical quantifier. - gener: From the Latin root gener- (stem of genus meaning "race, kind, birth, origin"), from the PIE root ǵenh₁- ("to beget, produce"). Functions as the core root relating to birth, family, or lineage. - ation: A suffix forming nouns of action or state from verbs, from Latin -ātiōn- (stem of -ātiō). Functions as a nominalizer, turning the concept into a noun form.