"fold" is a pretty common word in the business world.
Most dictionaries seem to list it, albeit with the "informal" tag.
If you think about the analogy of a bird spreading and folding its wings, or working with a folder open before you, I think the term makes good sense. Another reason it is popular is because the usual closing or shutting down tends to evoke the idea of a physical workplace to "shut down". Nowadays a lot of operations don't have that, so "fold" works perfectly. You close a business much like closing a folder.