I just found an old book in my storage boxes called : Hugo's Spanish Verbs Simplified . It's small , just 90 pages but I used to use it as a quick reference ... Incredible that it translates some things like ' Tú hubiste = thou hadst ' ! Or ' Tú habrías as thou wouldst ' . Vosotros habíais as you or ye had . This guide was published in London in 1905 . One passage reads as follows :

When speaking to one person , the only strictly grammatical form is 'thou' , 'thee' ; but nearly all nations have a special 'polite form of address' . In English , 'you' is substituted for 'thou' or 'thee' , 'your' for 'thy' etc.

The plural form 'you' probably originally implied that the person thus addressed was as good as two or more ordinary persons ; but in modern English the use of 'you , your , yours ' is so general , even when speaking rudely or abusively , that the politeness formerly impliedin the use of 'you' is quite lost . In polite Spanish , every untitled adult , of either sex , is habitually addressed as 'vuestra merced' ( your honour , your worship ) , the plural 'vuestras mercedes' being of course employed when more than one person is spoken to . Though somewhat strange to English ears , this form of address is fairly common in Ireland , and is really no more ridiculous than the English custom of addressing one person by the plural pronoun 'you' .

It goes on to say :

'Thou' and 'Ye' are seldom used , except by Quakers , and in scriptural language . The same cannot be said of 'tu' and 'vosotros' , as Spaniards habitually address NEAR RELATIONS , INTIMATE FRIENDS , ANIMALS and CHILDREN in the second person . But as any adult , even a beggar , is addressed as Vd. , the words 'tu' and 'vosotros' can hardly ever be employed with propriety by foreigners .

WOW ! This book is so interesting in how language has changed !