What does the “m” in bech32m stand for?

Question

I’ve looked at the mailing list, the BIP, commits that implement BIP350, the author’s twitter posts, and here on Stack Exchange, but couldn’t find an answer. Has it ever been publicly established what the “m” in bech32m stands for?

Answer 1

I believe I picked the name due to the fact that the difference between Bech32 and Bech32m is the introduction of a non-zero "M" constant, added to the checksum.

That constant (or the perceived need for one) existed before the name Bech32m was used. For example, this write-up was referenced in this mailinglist post in december 2019, and suggests the use of M = 0x3FFFFFFF. While the constant was changed later after further analysis, I believe the "m" in the name is in reference to the addition to that constant. In the BIP itself the constant is now called BECH32M_CONST, however.

The origin of "M" constant name itself I cannot remember, but it may well stand for "modifier" or "modified". So I guess it's fine to think of that as the meaning.