The story of what really happened to them that day gets 'curiouser and curiouser'. [=stranger and stranger]
The 'curious' [='inquisitive'] reader can find more information in the back of the book.
By a 'curious' coincidence, they bought a house the same day their old one burned down.
(..) And above all... ... all those who live without love. Professor, my mother's Patronus... ... was a doe, wasn't it? As the same as Professor Snape's. It's curious, don't you think? Actually, if I think about it... ... it doesn't seem curious at all! I'll be going now, Harry. Professor? (..)2011 Harry Potter and the Deathly Hallows: Part 2
(..) he's now Headmaster. Snape. He put a fake sword in Bellatrix's vault. Why? There are more than a few curious things in the vaults at Gringotts. And in Madam Lestrange's vault as well? Perhaps. I need to get into Gringotts. (..)2011 Harry Potter and the Deathly Hallows: Part 2