Those marchers walking back and forth outside a workplace with signs are picketing, and the word for it comes, oddly, from a pointed military stake driven into the ground.
To picket is to stand or march outside a workplace or other site, usually during a labor dispute, to protest, to publicize a grievance, and to discourage others from entering or doing business there. The people doing it form a picket line.
The word has a military root. A picket was originally a pointed stake, and then a soldier or small group posted on guard at the edge of a position, watching for the enemy. The protesters posted outside a struck workplace borrowed the name.
The picket line carries deep meaning in labor culture. To cross a picket line, to go in and work or shop despite the protest, is one of the strongest taboos in the movement, a betrayal of solidarity. Honoring the line is a basic act of mutual support.
It is protected speech, within limits. Peaceful picketing is a form of expression and assembly shielded by the First Amendment, though the law restricts tactics like blocking entrances or threatening violence. The line between protest and coercion is where much picketing law is fought.
