What does Hoppity-Hop mean?

It refers to a rabbit hopping around. . . hoppity hop. It is just a silly term.

It means 'to move in a hopping manner, like a rabbit, or a kangaroo'. Children's stories are often more direct and graphic in the way they describe things and rabbits (especially small ones) tend to 'hoppity-hop' rather than just 'hop'; caterpillars don't just 'crawl', they 'go creepy-crawly creepy-crawly'; snails and slugs 'go slippy-slidey' and so on! Notice that 'hiippetty-hop' and so on describe the movement itself and so are often combined with the verb 'go'. There's a certain delight in using these childish expressions and many a mother (and father) has told their child "Now, hippety-hop into bed!"! I'm pretty sure that your own language has similar 'childish' idioms which double the word to emphasize it in some way. 'to hop' is what we would normally say in English but 'to go hop, hop, hop' (or 'to go hoppity-hop') is more 'pictorial' and descriptive of the movement.