To have done something. This construction is mainly used for emphasis in short sentences that typically end with "so" or follow "so" with a verb. A: "You didn't brush your teeth like I asked you to." B: "I have so!" I have so asked Mom for permission, and if you don't believe me, you can ask her!
See also: have
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.