Originally, Physiologist was an ancient collection of stories about nature, which probably appeared in Alexandria in 200 - 300 A.D. The ancient Russian Physiologist (Russian: Физиолог) in its 15th-century version is a translation from Bulgarian. The Bulgarian version, in turn, was translated from Greek in the 11th - 12th century.

a biologist specializing in physiology

One who is versed in the science of physiology; a student of the properties and functions of animal and vegetable organs and tissues.

a scientist or medical doctor who studies how living organisms function