prig

A p[rig] is wise beyond his years in all the things that do not matter. A p. cracks nuts with a steam hammer: that is, calls in the first principles of morality to decide whether he may, or must, do something of as little importance as drinking a glass of beer. On the whole, one may, perhaps, say that all his different characteristics come from the combination, in varying proportions, of three things--the desire to do his duty, the belief that he knows better than other people, & blindness to the difference in value between different things. ["anonymous essay," quoted in Fowler, 1926]