pejoration

noun

1. depreciation; a lessening in worth, quality, etc.
2. Historical Linguistics. semantic change in a word to a lower, less approved, or less respectable meaning.Compare melioration(def 1).

noun

1. linguistics semantic change whereby a word acquires unfavourable connotationsthe English word “silly” changed its meaning from “holy” or “happy” by pejoration Compare amelioration (def. 3)
2. the process of worsening; deterioration

n.1650s, noun of action from pejorate (see pejorative).