English used to have polite and impolite you, like tu and vous in French, and only the polite you survived. ‘Thou’ is something you’d use either when addressing a friend, relative or insulting someone, say by calling someone ‘thou leprous cur!’
Just put 您 down as ‘polite you’ it’ll be fine.
Thanks! I’ll add “polite you” and/or “formal you”, as an alternative meaning to make things more clear.
I think in this case, there is a degree of semantic drift at play. Though “thou” was once considered more informal, due to the fact it is now associated with more archaic English, which is usually read in more formal settings (e.g., quoting of KJV Bible, Shakespeare) it is now considered more formal. Sort of like how in the article linked “terrific” once meant “inducing terror” and now means “wonderful”.