History of Hindi 'to'

[Varma]

I am researching the conjunction/discourse marker 'to' in modern Hindi and
would like to have a feel for the historical background.I have been unable
to find much help so far. Does anyone out there have any suggestions? Does
'to' descend from Sanskrit 'tatas' or 'tavas' or rather 'tu'? Does it have
more than one root? Is the saying true that 'tu' was often used to satisfy
metrical requirements in verse? Any ideas?
                        Terry Varma