Pretty good, in response to “How are things going?” This very modern-sounding phrase, which means one has nothing genuine to complain about (or at least will not admit it), comes from mid-nineteenth-century Britain. Eric Partridge cites an early example, R. S. Surtees’s Hawbuck Grange (1847), in which one character observes that time is passing lightly over another, who replies, “Middling—can’t complain.” Today it is a frequent response to inquiries about a business. See also fair to middling.