E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
Button-hole (A).
A flower inserted in the button-hole of a coat.
1
In fine wéather he [the driver of a hansom] will sport a button-holegenerally a dahlia, or some flower of that ilk.Nineteenth Century (March, 1893, p. 473).