boutonniere n : a flower that is worn in a buttonhole
A boutonnière is a flower or floral decoration worn by men. It is typically a single flower or bud. Traditionally, a boutonnière was worn pushed through the buttonhole of a jacket, but in modern times is often pinned onto a jacket lapel. The word comes from the French "boutonnière", from bouton which means "button". The British English term for this, "buttonhole," shows a literal translation of the original French.
While worn frequently in the past, boutonnières are now usually reserved for special occasions for which a dinner suit is standard, such as at proms, homecomings, funerals , and weddings. (Women who wear jackets on these occasions also often may wear 'buttonholes', but more typically a woman would wear a corsage.)
It is an American prom custom for the female to purchase the boutonniere for her male date and for it to match her dress and corsage. A bridegroom will almost always wear a boutonnière on his left lapel.
It is a British practice to place, after a wedding, the flowers from a buttonhole (together perhaps with other wedding flowers), on the grave of a recently deceased member of one of the families concerned.
boutonniere in German: Boutonniere (Blume)