I recently came across an excellent article in a 1992 festschrift for David Flusser on the possible origin of the “Jesus Fish” by Gedaliahu G. Stroumsa entitled, “The Early Christian Fish-Symbol Reconsidered.”
In the article, Dr. Stroumsa discusses some of the early studies on the origin of the Greek acronym ΙΧΘΥΣ (ichthus), and then presents his theory, which ties Jesus (whose Hebrew name is Yeshua or Joshua) to Joshua ben Nun, who led the Israelites into the “Promised Land.” Because נון (“nun“) in Aramaic means “fish,” and because there are several eschatological and messianic references to fish in Jewish literature (especially those linking the messiah to Jonah, who was swallowed by great fish only to be returned to life after three days, and those referencing that a leviathan would be eaten at a messianic meal), Stroumsa argues that the word ΙΧΘΥΣ first originated in Aramaic-speaking circles as a reference to the messiah, and only then, as what would become the orthodox Christian theology evolved, did the word become a convenient Greek mnemonic acronymic formula for Ἰησοῦς (Iēsous = “Jesus”), Χριστός (Christos = “Christ” or “anointed”), Θεοῦ (Theou = “of God” or “God’s”), Υἱός (huios = “Son”), Σωτήρ (sōtēr = “Savior”), first mentioned in Tertullian’s treatise On Baptism.
The article is well worth a read.
“The Early Christian Fish-Symbol Reconsidered.” in I. Gruenewald, Sh. Shaked and G. G. Stroumsa, eds., Messiah and Christos: Studies in the Jewish Origins of Christianity, in Honour of David Flusser ( Tübingen: Mohr Siebeck, 1992), 199-205. PDF