This is the second of a three-part question on the basilisk plot in Harry Potter and the Chamber of Secrets that I'm looking for CANON COMPLIANT explanations for. By "canon compliant", I mean within the spirit of canon, answers directly from the book(s), or quotes from J.K. Rowling.¹
- Professor Binns says, "The whole thing is arrant nonsense, of course," he said. "Naturally, the school has been searched for evidence of such a chamber, many times, by the most learned witches and wizards. It does not exist. A tale told to frighten the gullible." (CoS - page 151 - US Hardcover)
- Professor Binns also says, "Reliable historical sources tell us this much," he said. "But these honest facts have been obscured by the fanciful legend of the Chamber of Secrets. The story goes that Slytherin had built a hidden chamber in the castle, of which the other founders knew nothing. Slytherin, according to the legend, sealed the Chamber of Secrets so that none would be able to open it until his own true heir arrived at the school. The heir alone would be able to unseal the Chamber of Secrets, unleash the horror within, and use it to purge the school of all who were unworthy to study magic." (CoS - pages 150-151 - US Hardcover)
If none of the other three Founders were aware of the existence of Slytherin's Chamber, and Slytherin himself was keeping the existence of the Chamber a secret, how was the legend established?
¹ I find the Harry Potter Wiki to be inconsistent and oftentimes incorrect. I am not looking for any answer(s) from the HP Wiki. Just an FYI.