It's not clear why Eric Blair chose the name George Orwell. But even more puzzling is that we in Ipswich aren't clear about our river's names!
Correspondence in The Guardian speculated on whether George Orwell chose his name because he would have crossed the Orwell as a child when his parents took him on holiday to Southwold. Then someone pointed out that the Orwell Bridge wasn't built then and he would have crossed the Gipping en route from London, but George Gipping doesn't sound so good!
A further writer said that he would have seen the Orwell from the train or he could have crossed it by road because 'two of the three river crossings in the town are over the tidal Orwell, not the non-tidal Gipping.' But the Gipping is certainly tidal at Princes Street Bridge, and further upriver. Where does the name change? Stoke Bridge?