1817 Feb. 63/2 The elegant young man on whose account you consented to look interesting in your widow's cap.
1928 ‘Brent of Bin Bin’ xxii. 356 Adjusting her widow's cap like a war-bonnet, she arose to her full height of five-feet-one-and-a-half.
2001 (Nexis) 18 Jan. 3 Widow's caps were..usually trimmed with white crepe.