It's just the same principle as the use of the globes.

Where's the second boy ?' 'Please, sir, he's weeding the garden,' replied a small voice.
'To be sure,' said Squeers, by no means disconcerted.

'So he is.

B-o-t, bot, t-i-n, tin, bottin, n-e-y, ney, bottinney, noun substantive, a knowledge of plants.

When he has learned that bottinney means a knowledge of plants, he goes and knows 'em.