At first glance, this feels like one of Dickens's many "main character's name" style of titles. He's got Nicholas Nickleby, Martin Chuzzlewit, Oliver Twist, Barnaby Rudge, David Copperfield…and this one, Little Dorrit, which in the novel is the nickname of the main character, Amy Dorrit. It's a tried and true way of titling stuff: short, sweet, to the point, though maybe not a very good way of giving readers a sense of what's coming. We still do it today – check out Michael Clayton and its polar opposite, Zoolander.
But still. Why not just name it Amy Dorrit? It's not like girl names weren't selling back then (they had already had the runaway bestsellers Sybil and Mary Barton, after all). What does it do to take away that first name and swap in that strange adjective?
A couple of things come immediately to mind. First, we no longer know the gender of the main character. How many of you first thought Little Dorrit must be a boy? It's got kind of a Dorrit, Jr. ring to it, doesn't it? Second, we immediately wonder what's "little" about this character. Is it age – is the book going to be about a kid? Or is it size – are we talking a smaller-than-average human? Is it meant to be comparative – as in, that's the little Dorrit, not the big one? Or is it some less physical quality – is this going to be another one of Dickens's downtrodden tear-jerking sadsters? We don't know until we start reading, but all of these options are important to keep in mind. Any time you run across a young Dickensian woman whose first name is constantly getting misplaced or removed, that's a red flag to pay attention. (No, really, he does it a lot – check out Esther in Bleak House.)
Oh, and funny thing. Originally this novel was going to be called Nobody's Fault. That would have totally shifted our attention to the whole government-going-to-hell-in-a-handbasket plot rather than the Dorrit plot. Ultimately, Dickens decided that people prefer reading about human beings over giant institutions. (Still true today – a recent book on the Supreme Court is called The Nine, i.e. the judges themselves and not the branch of government.) But it feels like there's at least a little bit in common between the two, and that the "nobody" of the rejected title sort of matches up with the unnamed "little" of the title that went to press.