postern (n.)youdaoicibaDictYouDict[postern 词源字典]
late 13c., "back door, private door," from Old French posterne "side or rear gate," earlier posterle, from Late Latin posterula "small back door or gate," diminutive of Latin posterus "that is behind, coming after, subsequent," from post "after" (see post-).[postern etymology, postern origin, 英语词源]