The muscles of the body can be difficult to remember, as their names are often long and confusing. The key to learning the muscles is to understand the basic naming conventions, once you see the patterns, it will be much easier to remember.
Here are some of the basics of naming muscles
Deltoid - shaped like a triangle
Orbicularis - orbit, circular muscle
Major/Minor - large/small or sometimes upper and lower
Vastus - large
Dorsi or Dorsal - backside
Infra / Supra - lower and upper
Longis / Brevis - long/ short (brief)
Medialis / Lateralus - medial (toward the inside), lateral (toward the outside)
Some muscles are named for the region or the bone they are attached to, for example:
biceps femoris - two headed muscle attached to the femur
extensor carpi radialis longus - long muscle that runs the length of the radius (bone) to the carpals (wrist bones) that extends the fingers