The Greek word (ΙΧΘϒΣ) for fish was used in Christian antiquity as an acrostic formed by the initial letters of a primitive symbol of faith. When the word Savior (Σωτήρ) was added to the formula confessed by the Ethiopian eunuch whom Philip baptized (Acts 8.37), the acrostic was evident:Ιησο[symbol omitted]ς Χριστὸς Θεο[symbol omitted] ϒιὸς Σωτήρ, Jesus Christ, Son of God, Savior. There are abundant monumental and literary witnesses to the popularity of the formula. Tertullian (De Baptismo 1) spoke of Christians as "little fishes" (pisciculi ) like our "ΙΧΘϒΣ Jesus Christ." Application of the symbol to the Holy Eucharist is found in the inscriptions of abercius and pectorius; Pectorius bound together his first five verses with the acrostic. Other Eucharistic associations are found in funeral inscriptions, where, in at least one case, the formula is found thus: ΙΧΘϒΣ ΖΩΝΤΩΝ (the Fish of the living). The Christian Sibylline Oracles (bk. 8) make use of the acrostic for eschatological purposes.
See Also: acrostic.
Bibliography: h. leclercq, Dictionnaire d'archéologie Chretiénne et de liturgie (Paris 1907–53) 7.2:1990–2086. e. diez, Reallexikon für Antike und Christentum, ed. t. klauser (Stuttgart 1950–) 3:667–682. f. j. dÖlger, ΙΧΘϒΣ, v.1 (Münster 1910) 8–15, 87–182; v.2 (1922) 454–574. a. c. rush, Death and Burial in Christian Antiquity (Washington 1941) 86–87.
[m. c. hilferty]
"Ichthus." New Catholic Encyclopedia. . Encyclopedia.com. (October 19, 2018). http://www.encyclopedia.com/religion/encyclopedias-almanacs-transcripts-and-maps/ichthus
"Ichthus." New Catholic Encyclopedia. . Retrieved October 19, 2018 from Encyclopedia.com: http://www.encyclopedia.com/religion/encyclopedias-almanacs-transcripts-and-maps/ichthus