also boohoo, 1520s, originally of laughter or weeping (now only of weeping); see boo.
Online Etymology Dictionary, © 2010 Douglas Harper
Examples from the Web for boo-hoo
I used to long to throw myself in her lap and boo-hoo on her shoulder!The Dragon's Secret
Augusta Huiell Seaman
Monsieur, boo-hoo—we—ain't had nothin' to eat—since—morning.
At that moment the awfulness of her mistake dawned upon Mary, and she set up a loud 'Boo-hoo!'Baby Jane's Mission
Monsieur, we—boo-hoo—we asked that barber man over there to let us get warm in his store and—and—he wouldn't do—it—boo-hoo!
His boo-hoo might have been heard for miles, and the king naturally desired to stop it.The Old-Fashioned Fairy Book
Constance Cary Harrison