plume (oneself) on (something)
To pride oneself on something in a vain, boastful, or showy manner. He plumes himself on his business acumen, constantly talking about how many big sales he's pulled in and how much money he earns. But so much as challenge one of their worldviews with facts, and the aloof nonchalance these teenagers plume themselves on will crumple like tissue paper.
Farlex Dictionary of Idioms. © 2022 Farlex, Inc, all rights reserved.
Congratulate oneself, boast, as in He plumed himself on his victory. This idiom transfers the bird's habit of dressing its feathers to human self-satisfaction. [First half of 1600s]
See also: plume
The American Heritage® Dictionary of Idioms by Christine Ammer. Copyright © 2003, 1997 by The Christine Ammer 1992 Trust. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.