Euphemism

" friendly fire "
This is a term used to say when someone is shooting at their own team perhaps in a war or accidentally shooting at someone. It is used as a quick sharp phrase to shout out in war perhaps instead of using the long sentence of "you are shooting at your own team". It also softens up the meaning as it uses friendly which is not a aggressive word.

" to sleep with someone"
This is a term used as to when someone has had sex with someone else. This is used because saying sex straight up could be quite up front or shocking to some people making them feel uncomfortable so it used to make it less uncomfortable and easier to talk about, basically softening up what it means.

"Senior citizen"
This is a good term as it is used to talk about an old person. This is a good one because some people may take offence to saying old people and this softens it up. Not only does it soften it up but it makes the people sound more titled as they have a citizen class. It masks the fact that they are old and just classes them as a senior citizen.