V-form

In the Erzin dialect, children address their parents with the V-form; to use the T-form would show a lack of respect for parents.

Source: wiktionary

But cross-linguistically one finds that plural pronouns are predominant for the V-form. Again, there may well be a universal here that a plural address implies respect and that the singular pronoun implies a personal, i.e. intimate type of address.

Source: wiktionary

Typically, the informal pronominal address term (T-form) is the original second-person pronoun (Latin tu; Germanic du) and the polite or formal V-form is a plural form.

Source: wiktionary

... in March 2010 Ikea's Swiss website in German, French and Italian used the V-form except when addressing prospective job applicants.

Source: wiktionary