knock over vs tremble

knock over

verb

To bump or strike something in such a way as to tip it
To rob; to stage a heist of.

tremble

verb

To shake, quiver, or vibrate.
To fear; to be afraid.

noun

A shake, quiver, or vibration.

How often have the words knock over and tremble occurred in a corpus of books? (source: Google Ngram Viewer )