Buttonhole

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

Handicraft for Girls Idabelle McGlauflin
The Art of Disappearing John Talbot Smith
The Works of Rudyard Kipling: One Volume Edition Rudyard Kipling
The Bell-Ringer of Angel’s and Other Stories Bret Harte
The Night Side of London J. Ewing Ritchie
Werwolves Elliott O’Donnell
Textiles and Clothing Kate Heintz Watson
Old Valentines Munson Aldrich Havens
The Quaint Companions Leonard Merrick
Tommy and Co. Jerome K. Jerome

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