too big for one's britches

too big for (one's) britches

Overconfident in one's importance, skill, or authority; behaving as if one is more important or influential than one actually is. He's gotten too big for his britches ever since he got that promotion. John's been too big for his britches now that he's been scouted by pro teams.
See also: big, britches
Farlex Dictionary of Idioms.

too big for one's britches

Also, too big for one's boots. Conceited, self-important, as in Ever since he won that tournament he's gotten too big for his britches, or There's no talking to Jill anymore-she's just too big for her boots. This metaphoric idiom alludes to becoming so "swollen" with conceit that one's pants or boots no longer fit. [Late 1800s]
See also: big, britches
The American Heritage® Dictionary of Idioms by Christine Ammer.
See also:
  • britches
  • get too big for (one's) britches
  • drive (one) out of office
  • force (one) out of office
  • force out of office
  • give (one) (one's) head
  • give head
  • give somebody their head
  • give someone their head
  • cooking for one
References in periodicals archive
The man had grown too big for one's britches. When the election came, his party shrank.
Your 'PhD in politics'
barb if one got too big for one's britches. He was an old-fashioned letter writer who always returned one's correspondence.
JAMES W. VANSTONE 1925-2001
Yet, Coppola, like fellow movie brat Michael Cimino, represents the lesson learned in the "old" Hollywood: One can't get too big for one's britches, or too absorbed in one's own myth.
The Top 10 for the 20th Century: Film