From the French adosse, to lean, addorsed is a term that is applied to a motif with animals or objects placed back to back. Often observed in heraldic designs where lions, lambs or other animals are placed back to back for visual effect. Signatures and trademarks on jewelry are often a combination of back to back, addorsed, letters such as the back to back C’s Castellani used for his signature.

Castellani Mark with Addorsed C’s. c.1880.
Image courtesy of Wartski.