peg (one) as (something)
To believe or consider that one definitely is a certain type of person or thing. I pegged her as a total bore when she first started working here, but since getting to know her, she's actually pretty interesting. I'm disappointed, Jake—I never pegged you as a quitter.
See also: peg
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.
tv. to gossip about someone. Kim is always pegging Jill. What’s her problem?
McGraw-Hill's Dictionary of American Slang and Colloquial Expressions Copyright © 2006 by The McGraw-Hill Companies, Inc. All rights reserved.