Helen and T. S. Garp use the code word The Under Toad, a play on the word "undertow," for a very powerful feeling of dread that they often feel, especially Garp. In fact if there were one thing that Garp wishes for, it is that he could make the world safe for his children. As a parent, Garp is overly anxious, running after cars that drive too quickly through his neighborhood and peering into windows of homes where his son sleeps overnight.
It is this Under Toad against which Garp rails, but it is not until he is shot by the tongueless Pooh Percy that he feels somehow assured about the Under Toad and wishes that he could tell her to not be frightened of it anymore.
It surprise him to realize that the Under Toad was no stranger, was not even mysterious; the Under Toad was very familiar--as if he had always known it, as if he had grown up with it....The world was not safe.
Garp realizes that there is no need to be in fear of the Under Toad because it is something with which one lives every day. And, so, one must go on living; one must be grateful "for small favors"; one must savor life. There is life after Garp, he wants to tell his wife.