the center of the Earth
The deepest or innermost part.
down in the bowels of the Earth
The concept or quality that defines something at its very core.
the project's bowels
Chambers 20th Century Dictionary
bow′elz, n.pl. the interior parts of the body, the entrails, the intestines: the interior part of anything: (fig.) the heart, pity, tenderness (the emotions being supposed to be seated in the bowels—B. and Shak.).—v.t. Bow′el, to take out the bowels. [O. Fr. boel—L. botellus, a sausage, also an intestine.]
The numerical value of bowels in Chaldean Numerology is: 8
The numerical value of bowels in Pythagorean Numerology is: 4