What did Mr Shafter think of the Scowrers ? What was their other name. ( Act 1 scene 1-2)

From the text:

The boarding-house keeper instinctively sank his voice, as everyone did who talked about that terrible society. “The Scowrers,” said he, “are the Eminent Order of Freemen!”

Mr. Shafter was frightened of the Scrowers and their deeds, and he didn't want McMurdo staying in his boarding house because he was one of them.

“It's a murder society, that's vat it is.”

McMurdo laughed incredulously. “How can you prove that?” he asked.

“Prove it! Are there not fifty murders to prove it? Vat about Milman and Van Shorst, and the Nicholson family, and old Mr. Hyam, and little Billy James, and the others? Prove it! Is there a man or a voman in this valley vat does not know it?”

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But you vill find other lodgings, mister. I cannot have you here. Is it not bad enough that one of these people come courting my Ettie, and that I dare not turn him down, but that I should have another for my boarder? Yes, indeed, you shall not sleep here after to-night!”