Final answer:
Skeletal muscles are named based on criteria like shape, size, location, attachment points, number of origins, and action, exemplified by muscles such as the deltoid, named for its triangular shape, and rectus abdominis, named for the direction of its fibers.
Step-by-step explanation:
Anatomists have specific criteria for naming skeletal muscles that include their shape, size, location, attachments, number of origins, and action. For instance, the deltoid muscle is named for its large, triangular shape, resembling the Greek letter delta. Muscles such as the rectus abdominis are named for the direction of their fibers, running straight down the abdomen. The biceps brachii is an example where both the location and the number of origins (two in this case) contribute to the muscle's name. Criteria such as the location of a muscle relative to a bone or body region and the muscle's action, like flexion or extension, are also key in determining muscle nomenclature. Muscles like the flexor digitorum superficialis are named based on the action of flexing the fingers.