vastus
Like a strong hold, tenatious, the thing that is keeping it steady. The root is the but of the metaphor, so there isn't much to metaphorise about here: That which is strong, basic, raw- young and brutish. Characterised by strong holds and deep penetration.
Rumble. A Low, growling discontent. something is wrong. IT's like the shivers, but bigger, more powerful. It speaks of depth and might, larger than comprehension would allow. Fearful Majesty