‘I thought you inherited your money.’
‘I did, old sport,’ he said automatically, ‘but I lost most of it in the big panic – the panic of the war.’
I think he hardly knew what he was saying, for when I asked him what business he was in he answered, ‘That’s my affair,’ before he realized that it wasn’t the appropriate reply.
‘Oh, I’ve been in several things,’ he corrected himself. ‘I was in the drug business and then I was in the oil business. But I’m not in either one now.’

F. Scott Fitzgerald

The Great Gatsby. Chapter 5, Gatsby initially claimed that he inherited his money when his family died, but slips up here when speaking to Nick. He is not a good liar. To Nick that makes him a lot more honest than half the people who come to his parties.