Other name of Bay cyst is:

Apical Periodontal Cyst (Radicular Cyst, Periapical Cyst, Root End Cyst) There are two distinct variants of apical periodontal cysts, namely, those containing cavities completely enclosed in epithelial lining (True cysts), and those containing epithelium-lined cavities that are open to the affected root canals (bay cysts or pocket cysts). Reference: Shafer’s Textbook of ORAL PATHOLOGY Eighth Edition page no 76,77