pejoration (n.)

"deterioration, a becoming worse," 1650s, noun of action from pejorate (1640s), from Late Latin peiorare "make worse," from Latin peior "worse," perhaps originally "stumbling," from PIE *ped-yos-, suffixed (comparative) form of *ped- "to walk, stumble, impair," from root *ped- "foot." Meaning "a lowering or deterioration of the sense of a word" is by 1889.