The word chair came into English from the old French chaire created fom the Latin cathedra (cadeira --> chaere), which is related to the Greek ÎºÎ±Î¸ÎÎ´ÏÎ± (kathedra; chair, seat).
From the same root: cathedra, cathedral, ex cathedra
In modern Greek:
a) ÎºÎ±Î¸ÎÎ´ÏÎ±: cathedra [kathedra]
Î²) ÎºÎ±Î¸ÎµÎ´ÏÎ¹ÎºÏŒÏ‚ (Î½Î±ÏŒÏ‚): cathedral [kathedrikos naos]
Î³) Î±Ï€ÏŒ ÎºÎ±Î¸ÎÎ´ÏÎ±Ï‚: ex cathedra [apo kathedras]
ÎºÎ±Î¸ÎÎ´ÏÎ± (kathedra) - cathedra --> cadeira --> chaere --> chaire --> chair
See the blog 'English words of no apparent Greek origin' at: http://ewonago.blogspot.com/