不是雅号，而是军队中的官职的名称。就像今天的师长、军长。

是中国古代的一种官职，还有右卫将军，前卫将军，后卫将军。不同朝代叫法不一。

不是雅号。It's a formal title used in 三国时期（或前后）. It‘s a quite high-level military officer. when there is 左 or 右 in titles, it often indicates that the power are divided to 2 parts，if there are左and右and中，then power is divided to 3 parts.（power rank：中>右>左） so 将军means he's a military officer，左卫 indicates how many soldiers are under him.(half of the army of the capital city) so put it together, 左卫将军is a military title. 卫 means guard，you may already know.

http://baike.baidu.com/link?url=4lk1Ua_B2mDGhj8yl45y1RZA6zBGshWQTqYXAHic4S51vL3xbffyd1O5DV44xtHcDlNk_hq8YjGvK3wVD9Z3wa

是军队里的官职，类似现在的军官