Development of two singular pronouns of address in European languages (Brown and Gilman 1972):

Languages
T Pronoun
V Pronoun
Italian
tu
voi> lei
French
tu
vous
Spanish
tu
vosotros > usted
German
du
sie
English
thou
ye > you

Pronouns of address in English:

Singular
Plural
Singular of reverence
Old
thou/thee
ye (NOM)> you (ACC)
you
New
you
you
N/A