Question

alter ego
alter ego  
n.（名词）
1.Another side of oneself; a second self.
    个性的另一面；第二自我
2.An intimate friend or a constant companion.
    亲密朋友，长期伙伴
ORIGIN
1.Latin
    拉丁语
2.alter [other]
    alter [其它的]
3.ego [I, self]
    ego [我，自我]