It's the way Tess lobs her questions out, apropos of nothing. Her random reasoning finds a leaping-off point, and she asks:
1) When little crabs pince you, is it tickle-y? Just little ones?
2) What is under everybody's floor? Just old 'wubbish?
3) When people die, do they never come back? Not ever?
Ah, the everyday parental sport of hiding the lump in your throat.