"***** and babes took center stage Wednesday morning as nursing mothers held “nurse-ins” at Target stores across the country to assert their right to breast-feed their children in public."
The phrase probably comes from 'sit-in', from the UK in the 1930s, when trade unionists would sit in their workplace - on strike - refusing to work but nevertheless occupying their workplace
From there, you can use the '-in' suffix to mean any protest. Nursing mothers can hold a nurse-in to protest if breast-feeding is restricted or looked down upon. I agree with their prote