The story
From Ancient Greek δεχ- (dekh-, “to take, receive”) + -tic + a shortening of Ancient Greek αἰτιατική (aitiatikḗ, “accusative”) + -ive, intended to suggest "recipient-as-accusative", with the spellings of Greek components latinized. The term was first introduced by Edward L. Blansitt Jr. (1984). A more current term with the same signification is secundative.
Etymology from Wiktionary, CC BY-SA 4.0.