on one‘s back 和in one's back区别如题,并说明意思不想加几个单词,就原来的意思

问题描述:

on one‘s back 和in one's back区别
如题,并说明意思
不想加几个单词,就原来的意思

be on one's back(=be ill in bed) 卧病不起.
in one's back pocket 囊中之物