Answer:
Idiom
Step-by-step explanation:
As nouns the difference between idiom and euphemism is that idiom is a manner of speaking, a way of expressing oneself while euphemism is (uncountable) the use of a word or phrase to replace another with one that is considered less offensive, blunt or vulgar than the word or phrase it replaces.
Example:
Instead of using
You're just a *****
you would use
You're just a scaredy-cat.
That would be a euphemism