a round robin

a ˌround ˈrobin

a letter of protest, etc. that has been signed by many people in such a way that no single person can be blamed or punished for sending it: Did you sign that round robin that was sent to the manager this week?This comes from the navy. Originally it was a letter of protest in which the signatures were written in a circle so that nobody could see who had signed it first.
See also: robin, round