euphemism or dysphemism

eu·phe·mism

/ˈyo͞ofəˌmizəm/

noun

noun: euphemism; plural noun: euphemisms

a mild or indirect word or expression substituted for one considered to be too harsh or blunt when referring to something unpleasant or embarrassing.

"“downsizing” as a euphemism for cuts"

 

dys·phe·mism

/ˈdisfəˌmizəm/

noun

noun: dysphemism; plural noun: dysphemisms

a derogatory or unpleasant term used instead of a pleasant or neutral one, such as “loony bin” for “mental hospital.”