The explanation is pretty boring. If you look at https://superuser.com/questions/421997/what-is-a-ssh-key-fingerprint-and-how-is-it-generated it's explained that some fingerprints are displayed with Base64, which according to https://en.wikipedia.org/wiki/Base64 allows the use of all 26 letters of the alphabet, and both the complete uppercase and lowercase sets.

So basically it's just random chance that a given fingerprint has some data that shows up as a word.

SSH keys can likewise use base64, e.g. for PEM format, as per https://unix.stackexchange.com/questions/492704/what-encoding-is-used-for-the-keys-when-using-ssh-keygen-t-rsa