falter vs tremble

To waver or be unsteady; to weaken or trail off. 

To fail in distinctness or regularity of exercise; said of the mind or of thought. 

To hesitate in purpose or action. 

To cleanse or sift, as barley. 

To stammer; to utter with hesitation, or in a weak and trembling manner. 

To stumble. 

To lose faith or vigor; to doubt or abandon (a cause). 

To shake, quiver, or vibrate. 

To fear; to be afraid.