What does "would" mean in "would yeh know anythin' about it?"

Question

"Hullo, Bane," said Hagrid. "All right?"
"Good evening, Hagrid, I hope you are well?"
"Well enough. Look, I've jus' bin askin' Ronan, you seen anythin' odd in here lately? There's a unicorn bin injured –– would yeh know anythin' about it?"
(Harry Potter and the Sorcerer's Stone)

I’m wondering what the sentence would mean that has ‘would’ instead of ‘do’.

Answer 1

CopperKettle's comment that this is "probably a polite way of asking" is probably correct.

Qualifying a question in this manner is intended to reduce a) the sense that an answer is demanded of your hearers or b) the implication that your hearers are somehow involved in the matter into which you are inquiring. The more tentativity and contingency you can introduce into your sentence, the more you are distancing the demand or the implication. You are deferring to your hearers, leaving it to them how or whether they will respond:

• What do you know about it?
• Do you know anything about it?
• Would you know anything about it?
• Would you happen to know anything about it?
• I was wondering if you know anything about it?
• I was wondering if you might know something about it?
• It occurred to me to wonder if perhaps you might happen to have come across some stray fact, or even mere rumour, which would suggest a potentially valuable line of inquiry I might pursue in trying to find out about it?