means To shake involuntarily with small, quick movements, usually from fear, cold, weakness, or strong emotion.

from From Old French 'trembler,' descending from Latin 'tremulare,' to quiver — itself rooted in 'tremere,' to shake or quake. That Latin 'trem-' is a deep Indo-European root for trembling, the same family that gives us 'tremor' and 'tremulous.' The word has been shivering its way through the language for centuries, always keeping that sense of motion too fast and too small to control.