What does Bay mean?
Bay /bay/ as a boys' name (also used as girls' name Bay). Geography name: an indentation of land in a coastline. Also generally a short form of Bailey, although it is sometimes used as an independent given name.
Affiliated boy name: Bayard.
How popular is Bay?
Bay is an uncommon first name for men but a very popular surname for all people (#5071 out of 150436, Top 3%). (2000 U.S. Census)
Below is a charted comparison of the usage of Bay and related names. The only prominent related form of Bay (not in Top 1000) listed in the Top 1000 is Bailey. Other variants, like Baily, are seldom used. This relation of Bay was at the apex of its popularity in 1997 (adoption of 0.849%) and has become much less common since. (2014 Birth Statistics)