means a state of great disturbance, confusion, or agitation, whether in the world around you or the mind within.

from An English word from the 16th century, of obscure birth. The popular guess links it to the French 'tremouille' — the hopper of a mill that constantly shakes grain — but that connection is unproven. Its early sense was the bustle and commotion of toil and trouble, and the word itself has never quite settled down, fittingly enough.