His name means 'He of appeasement', and he is nothing else. He is merely the personified shadow or dream generated by the emotion of the ritual very much, to take a familiar instance, as Father Christmas is a 'projection' of our Christmas customs. The Thesmophoria formed the great festival of Demeter and her daughter Korê, though here again Demeter appears with a clinging epithet, Thesmophoros.
From beings like Thesmophoros and Meilichios the road is of course much easier. They are already more than half anthropomorphic; they only lack the concreteness, the lucid shape and the detailed personal history of the Olympians. But even in daily life primitive men seem to have dealt more freely than we generally do with apparitions and voices and daemons of every kind.