Brōoch1, n.
(brōch) (Synop., § 130), n. [See BROACH.]
Sense 1. An ornament, in various forms, sometimes set with jewels, with a tongue, pin, or loop, for attaching it to a garment; usually worn on the breast. It is sometimes mentioned as an ornament worn in the hat.
Honor's a good brooch to wear in a man's hat at all times. B. Jonson.
Sense 2. (Paint.) A painting all of one color, as a sepia painting, or an Indian ink painting.