what does "under them bonnets"mean? He had not known his father was watching. He was tense. He jerked his pole cautiously and the bob flipped across the water. There was a swirl, a silver form shot half clear of the water, an open mouth as big as a cook-pot enveloped the bob. A weight like a millstone dropped at the end of his line, fought like a wild-cat, and pulled him off-balance. He braced himself against the frenzy to which he was irrevocably attached. Penny called, "Take it easy. Don't let him git under them bonnets. Keep the tip o' your pole up. Don't give him no slack."