This term is incorrectly spelled [annulus] in most literature. The proper term [anulus] is a derivative of Latin and means "ring" or "circle". The term anulus was adopted by anatomists worldwide in 1955, with the publication of the Nomina Anatomica (Paris). The plural for for anulus is anuli.

There are many ring-like structures or anuli in the human body:

• anulus inguinalis superficialis: Superficial inguinal ring
• anulus inguinalis profundus: Deep inguinal ring
• anulus fibrosus: Center region of an intervertebral disc
• anulus lymphaticus pharyngis: Pharyngeal lymphoid ring or ring of Waldeyer , etc.

Sources:
1. "The origin of Medical Terms" Skinner, AH, 1970
2. "Terminologia Anatomica: International Anatomical Terminology (FCAT)" Thieme,1998
3. "Gray's Anatomy"38th British Ed. Churchill Livingstone 1995
4. "The Doctor's Dyslexicon" Dirckx, JH;Am J Dermatopathol 2005;27:86–88