euphemism

the substitution of a mild, indirect, or vague expression for one thought to be offensive, harsh, or blunt

dysphemism (or cacophemism)

the substitution of a harsh, disparaging, or unpleasant expression for a more neutral one

orthophemism

the use of a neutral expression to mean exactly what it says

Some examples of orthophemisms from recent #code4lib conversations:

It’s time for the afternoon banana.

They’re burning the popcorn early today.

I held her Grammy.