动词 backdate:

1. make effective from an earlier date

backemfn.反电动势backn.后面；背脊；靠背；后背；后卫vt.支持；后退adv.向后地adj.向后的；后面的；偏远的；过时的；积欠的back-action plugger[医] 回力充填器back-strike printer背击式打印机, 后击式打印机backwash waste outlet返洗液废水出口back-formation word逆生词back-up for wehting焊接衬垫back-scattered dose反散射辐射剂量back stepping control反演控制back-ring structure加强环back-point removing背向点剔除back titration method返滴定法

1. His family goes back to the 18th century.
   他的家族可追溯至十八世纪。
2. He is plagued by demons which go back to his traumatic childhood.
   他为心魔所困扰，那可追溯至他饱受创伤的童年。