euphemism

Concise Oxford English Dictionary © 2008 Oxford University Press:
euphemism /ˈjuːfəmɪz(ə)m/

▶noun a mild or less direct word substituted for one that is harsh or blunt when referring to something unpleasant or embarrassing.

– derivatives
euphemistic adjective,
euphemistically adverb,
euphemize (or euphemise) verb.

– origin C16: from Gk euphēmismos, from euphēmizein ‘use auspicious words’, from eu ‘well’ + phēmē ‘speaking’.