User blog comment:B214/Volume 22 spoilers/@comment-83.27.153.180-20160721093944/@comment-9595671-20160721210128

And if she is part of the Old Satans' descendants, then her name makes sense disguise wise because Lessthan seems very similar in both spelling and pronounciation to Leviathan.

The only reason no one's porbably considered that in universe is because Lessthan sounds kinda ridiculous and would probably make people laugh at it rather than think deeply about it, which could be her intention.