Source unknown, probably combination of Christian symbols circle and triangle. The inclusion in Glagolitic of the lettersⰊ,Ⰹ andⰋ with the same phonetic value was probably intended to imitate Byzantine Greek orthography where bothη(eta) andι(iota) were pronounced as /i/; it is possible that in the oldest textsⰋ rendered thei that alternated with tenseь.
i