pátsi comes from the Medieval Greek expression (min)pas-ce (with raising of the unstressed /e/ and tsitacism, Ralli 2017).
E.g. pátsi pas z-mitiʎíɲ tútiɲ t-vðumáða?
min-pas-ce pas sti mitilíni túti tin evðomáða?
‘Will you be going to Mytilene this week?’