Answer: I think it should be, "The poet has something to hide."
Because he/she is hidding his/her identity by saying he/she is nobody. Then the poet is showing a panic behaviour which is often found when someone is lieing or hidding anything.
This also creates a sort of humour that the poet shows when he is messing around the person who has actually caught him sneeking around or doing something suspicous.
Also, banish is a word which is usually used during the king's and queen's rulling periods. That is what usually they would do in the historical times where a king or queen would banish someone if they had done a serious sin or upsetted anyone.