interpretative (adj.)

late 14c., "expound the meaning of, render clear or explicit," from Old French interpreter "explain; translate" (13c.) and directly from Latin interpretari "explain, expound, understand," from interpres "agent, translator," from inter "between" (see inter-) + second element probably from PIE *per- (5) "to traffic in, sell." Related: Interpreted; interpreting.

1670s, from interpret + -ive, perhaps on model of assertive or other like words, where the -t- belongs to the Latin stem. The preferred formation is interpretative. Listed by Fowler among the words "that for one reason or another should not have been brought into existence."