a richly ornamented, triangular piece of cloth formerly worn, esp. by women, as a covering for the chest and abdomen
Origin of stomacherMiddle English stomachere: see stomach and -er
A heavily embroidered or jeweled garment formerly worn over the chest and stomach, especially by women.
1616 portrait of Justina van Teylingen by Cornelius van der Voort (1576-1624)
Apparently from stomach +"Ž -er, perhaps after Middle French estomachier.