Deprecation

[L. deprecatio; cf. F. déprécation.]

1. The act of deprecating; a praying against evil; prayer that an evil may be removed or prevented. [archaic]

Humble deprecation.

2. Entreaty for pardon; petitioning.

3. An imprecation or curse. [Obs.] Gilpin.

4. A strong expression of disapprobation; an expression of a low opinion.
[PJC]

noun

The act or an instance of belittling: belittlement, denigration, depreciation, derogation, detraction, disparagement, minimization. See attack/defend, show/hide.

The noun has 2 meanings:

Meaning #1: a prayer to avert or remove some evil or disaster

Meaning #2: the act of expressing disapproval (especially of yourself)
  Synonym: denigration