Button-hole

the hole, slit, or loop through which a button is passed and by which it is secured.
Chiefly British. a boutonniere.
Surgery. a short, straight incision through the wall of a cavity or a canal.
to sew with a buttonhole stitch.
to make buttonholes in.
to hold by the buttonhole or otherwise abruptly detain (someone) in conversation:
The reporter tried to buttonhole the mayor for a statement on the bus strike.
Historical Examples

Two banks of the Seine Fernand Vandrem
Red Rose and Tiger Lily L. T. Meade
As A Chinaman Saw Us Anonymous
For The Honor Of France Thomas A. Janvier
Hilda Sarah Jeanette Duncan
Punchinello, Vol. 1. No. 20, August 13, 1870 Various
Manners and Rules of Good Society Anonymous
The Stark Munro Letters J. Stark Munro
Dusty Diamonds Cut and Polished R.M. Ballantyne
The Eternal City Hall Caine

noun
a slit in a garment, etc, through which a button is passed to fasten two surfaces together
a flower or small bunch of flowers worn pinned to the lapel or in the buttonhole, esp at weddings, formal dances, etc US name boutonniere
verb (transitive)
to detain (a person) in conversation
to make buttonholes in
to sew with buttonhole stitch
n.