pejoration
noun
pe·jo·ra·tion
plural -s
: a change for the worse : depreciation
specifically : an historical process by which the semantic and connotative status of a word tends to decline compare melioration
Word History
Etymology
Medieval Latin pejoration-, pejoratio, from Late Latin pejoratus (past participle of pejorare to become worse, make worse) + Latin -ion-, -io -ion