buffer; something to soften the blow
Wasei-eigo from 'one cushion'; used for an intermediate step, person, or thing that reduces direct impact or confrontation.
wasei-eigo (Japanese-coined English), from one cushion
If you say it directly it might cause friction, so it's better to put a buffer in between when you tell them.
Before talking to the boss, I had a senior colleague act as a buffer.