from the GNU version of the Collaborative International Dictionary of English
- n. That part of the skeleton connected with the sense organs and the viscera.
from The Century Dictionary and Cyclopedia
- n. The splanchnic or visceral skeleton; those hard parts of the body, collectively considered, which are developed in special relation with the viscera, and serve to support or contain them.
Sorry, no etymologies found.
They had no direct connection with the vertebral column, and seemed therefore to belong to what Carus  had called the visceral or splanchno-skeleton.