soleus

[soh-lee-uh s]

noun, plural so·le·i

[soh-lee-ahy] /ˈsoʊ liˌaɪ/, so·le·us·es.

a muscle in the calf of the leg, behind the gastrocnemius muscle, that helps extend the foot forward.

Origin of soleus

1670–80; < New Latin, masculine derivative of Latin solea sandal; see sole²

Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

Then she raised one of them, and her fingers explored the common tendon of the soleus and gastrocnemius.
Gray youth
Oliver Onions
On the back of the leg the most important muscles, forming what is known as the calf, are the gastrocnemius and the soleus.
A Practical Physiology
Albert F. Blaisdell
Here the artery is separated from the inner border of the tibia, by the flexor longus digitorum, and is covered by the soleus.
A Manual of the Operations of Surgery
Joseph Bell
Professor Pancoast divides the inferior portion of the soleus muscle instead of the tendo Achillis.
A Manual of the Operations of Surgery
Joseph Bell

muscle of the calf of the leg, 1670s, Modern Latin, from Latin solea "sole" (see sole (n.1)). So called for its flatness.