Plaid (noun) : a rectangular length of tartan worn over the left shoulder as part of the Scottish national costume.
The Shawl by Louise Erdrich
“Soon, she couldn’t rise to cook or keep the cabin neat, and it was too much for the girl, who curled up each night exhausted in her red-and-brown plaid shawl, and slept and slept, until the husband had to wake her to awaken her mother, for he was afraid of his wife’s bad temper, and it was he who roused Aanakwad into anger by the sheer fact that he was himself and not the other.”
This statement explains how the wife is very tough women and has a bad temper. Therefore, she got tired of the housework and she gets covered to her plaid material shawl and tries to relax for a long time. When her husband notices it and she gets very annoyed with him.