1640s; see erupt + -ive. Perhaps from French éruptif.
Entries linking to eruptive
erupt v.
1650s, of diseases, etc., from Latin eruptus, past participle of erumpere "to break out, burst," from assimilated form of ex "out" (see ex-) + rumpere "to break, rupture" (see rupture (n.)). Of volcanoes, from 1770 (the Latin word was used in reference to Mount Etna). Related: Erupted; erupting.
-ive
word-forming element making adjectives from verbs, meaning "pertaining to, tending to; doing, serving to do," in some cases from Old French -if, but usually directly from Latin adjectival suffix -ivus (source also of Italian and Spanish -ivo). In some words borrowed from French at an early date it has been reduced to -y (as in hasty, tardy).