fluctuate vs shilly-shally

fluctuate

verb

To undulate.
To cause to vary irregularly.
To vary irregularly; to swing.
To be irresolute; to waver.

shilly-shally

verb

To vacillate.
To procrastinate.

adj

Indecisive; wavering.

noun

Indecision; irresolution.

How often have the words fluctuate and shilly-shally occurred in a corpus of books? (source: Google Ngram Viewer )