'pseudo-messiah' is built from the Greek prefix 'pseudo-' (from Greek 'pseûdos') meaning 'false' and 'messiah' (from Hebrew 'māšîaḥ' via Greek and Latin) meaning 'anointed one'.

'messiah' passed from Hebrew 'māšîaḥ' into Greek as 'Messías' and Latin as 'Messias', then into Middle English and modern English as 'messiah'; 'pseudo-' comes from Greek 'pseûdos' and entered English as a productive prefix meaning 'false' or 'pretend', forming compound terms such as 'pseudo-messiah'.

Originally 'messiah' meant 'anointed one'; combined with 'pseudo-' the compound has come to mean 'a false or pretended anointed one' (i.e., a false savior).