c. 1840, in logic, "make explicit the use of a term in a proposition by attaching all, some, etc.," from Modern Latin quantificare, from Latin quantus "as much," correlative pronominal adjective (see quantity) + combining form of facere "to make" (from PIE root *dhe- "to set, put"). Literal sense of "determine or mark the quantity of, measure" is by 1878. Related: Quantified; quantifying.

"that may be measured with regard to quantity," 1868, from quantify + -able. Related: Quantifiably.

"act of attaching quantity to; act of determining the quantity," 1847, noun of action from quantify. Related: Quantificational.