buttonhole (someone)
To confine or accost someone in or with conversation. Likened to holding onto someone by the lapels (on which the buttonhole used for a boutonniere is located). I tried to leave the office early, but Larry buttonholed me with a tedious conversation about weekend plans.
buttonhole someone
Accost or detain a person in conversation. For example, The reporter tried to buttonhole the senator, but she got away. This term is a metaphor for literally grasping someone by a buttonhole on his or her clothing. [Mid-1800s]