The word chair came into English from the old French chaire created fom the Latin cathedra (cadeira → chaere), which is related to the Greek καθέδ?α (kathedra; chair, seat).
From the same root: cathedra, cathedral, ex cathedra
In modern Greek:
a) καθέδ?α: cathedra [kathedra]
β) καθεδ?ικός (ναός): cathedral [kathedrikos naos]
γ) από καθέδ?ας: ex cathedra [apo kathedras]
καθέδ?α (kathedra) - cathedra → cadeira → chaere → chaire → chair
See the blog ‘English words of no apparent Greek origin’ at: http://ewonago.blogspot.com/