Which is the crux of it all - there's no way to optimize the search of the key space to generate only keys that already have a set prefix. Rejection sampling ca

Which is the crux of it all - there's no way to optimize the search of the key space to generate only keys that already have a set prefix. Rejection sampling can target anything, no matter if someone (or some dictionary) applies a meaning to the specified sequence. As another thought experiment, imagine using a true random source to generate a BTC priv key whose base58-represented P2PK address happened to spell out "1money". Would it be less entropic than if it were on purpose searched for and found using e.g. VanityGen? Or less entropic than some random characters like "1trwm"? Certainly not. By a total coincidence the word "trwm" is Welsh for "heavy".