Gawain Gaiter is Susan Sto Helit's charge as Nanny/Governess in Hogfather. He is the brother to Twyla Gaiter and has a large vocabulary for his age, so large that Susan has him reading Callus Tacticus's journals. He can be unbearably twee, just like his sister, when he wants something, but Susan is weaning him off his precociousness. He loves watching the impossible (to adult eyes) happen and uses all the ludicrous stories told by the previous governess to have them come true. He deliberately steps on all the cracks he can find to summon forth the bears that eat you up, forcing Susan to beat them into submission. He is a typical child, with all the unthinking cruelty and black-and-white right and wrong that are so characteristic of the under-sevens.
At the end of the events of 'Hogfather', Teatime's scrying crystal glass eye ends up in Gawain Gaiter's possession; he found lying in the fireplace after Teatime's body had been removed and mistook it for a marble, after with which he never lost a game with it.
Gawain is the kind of posh prattish name chosen by parents who are vaguely educated in the classics and want a name that shows their offspring as a cut above the ordinary, overtones of King Arthur and the Round Table guaranteed to make the child a target on the school ground. When Death visited Susan at the Gaiters, and asked her "Why Gawain?", she hazarded "I... suppose it's a good strong name for a fighter..." "A self-fulfilling prophecy I suspect," was Death's response, implying that Gawain is going to have to be a fighter because others will ridicule his name which will inevitably lead to the occasional dust-up, especially whilst he is still a child. The similarity to the Johnny Cash song "A boy named Sue" is obvious.