1580s, "one who or that which modifies," agent noun from modify. Grammatical sense of "word, phrase, or clause which modifies another" is from 1865.
Entries linking to modifier
modify v.
late 14c., modifien, "alter, amend, adjust, change the properties, form, or function of;" also "set limits, keep within the bounds of reason; choose a middle course," from Old French modifier (14c.), from Latin modificare "to limit, measure off, restrain," from modus "measure, manner" (from PIE root *med- "take appropriate measures") + combining form of facere "to make" (from PIE root *dhe- "to set, put"). Related: Modified; modifying.