too big for one's britches

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
References in periodicals archive ?
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.