late 15c., "to repeat, produce a second (like the first);" 1620s, "to double," from Latin duplicatus, past participle of duplicare "to double," from duo "two" (from PIE root *dwo- "two") + plicare "to fold" (from PIE root *plek- "to plait"). Related: Duplicated; duplicating.
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).
<a href="https://www.etymonline.com/word/duplicative">Etymology of duplicative by etymonline</a>
Harper, D. (n.d.). Etymology of duplicative. Online Etymology Dictionary. Retrieved $(datetime), from https://www.etymonline.com/word/duplicative