The exhortation grab a root and growl is a way of telling someone to buck up and do what must be done. The sense of grabbing and growling here suggests the kind of tenacity you might see in a terrier sinking his teeth into something and refusing to let go. This phrase is at least 100 years old. A much more rare variation is grab, root, and growl. Both expressions are reminiscent of a similar exhortation, root, hog, or die. This is part of a complete episode.