"Incredulousness" is a word in ENGLISH

The state or quality of being i/credulous; a withholding or refusal of belief; skepticism; unbelief; disbelief.

Indicating, or caused by, disbelief or incredulity.

Incredible; not easy to be believed.

Not credulous; indisposed to admit or accept that which is related as true, skeptical; unbelieving.

In an incredulous manner; with incredulity.

To doubt of; to regard with incredulity.

The withholding of belief; doubt; incredulity; skepticism.

One who does not believe; an incredulous person; a doubter; a skeptic.

Not believing; incredulous; doubting; distrusting; skeptical.