Relevance of the word 'ICTHUS'

Entry from The Oxford Dictionary of the Christian Church (3rd ed.):

Fish (Gk. ἰχθύς).In Christian art and literature the fish is a symbol of Christ, also sometimes of the newly baptized and of the Eucharist. It came into use in the 2nd cent., but neither its origin nor its meaning have so far been completely elucidated. It occurs in *Tertullian’s ‘De Baptismo’, where the writer compares the neophytes to little fishes, following the Fish, in connection with the idea of the second birth in the waters of Baptism. This image is found also in the ‘Shepherd’ of *Hermas, in the Inscription of *Abercius, in *Clement of Alexandria, and in many other old Christian documents; but it is doubtful whether the symbol is exclusively Christian or influenced by Babylonian and Indian mythology. Opinions are also divided as to whether the symbol is derived from the acrostic ΙΧΘΥΣ = Ἰησοῦς Χριστός Θεοῦ Υἱὸς Σωτήρ (‘Jesus Christ, Son of God, Saviour’),or the acrostic from the symbol. The acrostic is frequently held to have originated in *Gnostic circles, since it is found in the ‘*Sibylline Oracles’. In the 4th and 5th cents. the fish became an emblem also of the Eucharist, and is frequently found in the paintings of the *catacombs in combination with bread and wine. In recent years, in some parishes of the Church of England certain associations willing to help those in need have adopted the symbolism of a fish.

SOURCE: F. L. Cross and Elizabeth A. Livingstone, The Oxford Dictionary of the Christian Church, 3rd ed. rev. (Oxford; New York: Oxford University Press, 2005), 617.

_{Additional Resources: J. B. *Pitra, OSB, Spicilegium Solesmense, 3 (Paris, 1855), pp. 499–543 (‘ΙΧΘΥΣ, sive de Pisce Allegorico et Symbolico’); G. B. *de Rossi, ibid., pp. 545–84 (‘De Christianis Monumentis ΙΧΘΥΝ exhibentibus’); H. Achelis, Das Symbol des Fisches and die Fischdenkmäler der römischen Katakomben (Marburg, 1888); R. Pischel, ‘Der Ursprung des christlichen Fischsymbol’, Sb. (Berl.), 1905 (1), pp. 506–32; C. R. Morey, ‘The Origin of the FishSymbol’, Princeton Theological Review, 8 (1910), pp. 93–106, 231–46, and 401–32; 9 (1911), pp. 268–89; 10 (1912), pp. 278–98. I. Scheftelowitz, ‘Das Fisch-Symbol im Judentum and Christentum’, Archiv für Religionswissenschaft, 14 (1911), pp. 1–53. F. J. Döger, ΙΧΘΥΣ (vol. 1, RQ, Suppl. 17; 1910; 2nd edn., Münster i.W., 1928; vols. 2–5, ibid., 1922–43). L. Werhahn Stauch, ‘Christliche Fischsymbolik von den Anfängen his zum thohen Mittelalter’, Zeitschrift für Kunstgeschichte, 35 (1972), pp. 1–68. R. St J. Tyrwhitt in DCA 1 (1880), pp. 673 f, s.v., and pp. 625–8, s.v. ‘Eucharist (in Christian Art)’; F. Cumont in PW 9 (pt. 1; 1914), cols. 844–50, s.v. ‘Ichthys’; H. *Leclercq, OSB, in DACL 7 (pt. 2; 1927), cols. 1990–2086, s.v. ΙΧΘΥΣ; J. Quasten in NCE 5 (1967), pp. 943–6, s.v. ‘Fish, Symbolism of’; J. Engemann in RAC 7 (1969), cols. 1021–97, s.v. ‘Fisch, B. Christlich’.}

Acronym:

᾽Ιησοῦς

Χριστος

Θεοῦ

Υἰὸς

Σωτήρ

Jesus

Christ

(of) God

Son

Savior

ΙΧΘΥΣ means fish in an old form of Greek. It now primarily refers to a particular Christian fish symbol. From Wikipedia:

Ichthys (also Ichthus or Ikhthus /ˈɪkθəs/), from the Koine Greek word for fish: ἰχθύς, (capitalized ΙΧΘΥΣ or ΙΧΘΥϹ) is a symbol consisting of two intersecting arcs, the ends of the right side extending beyond the meeting point so as to resemble the profile of a fish, used by early Christians as a secret Christian symbol and now known colloquially as the "sign of the fish" or the "Jesus fish."

The word itself has symbolic meaning, though. Saint Augustine gives the following symbolic explanation in City of God:

But if you join the initial letters of these five Greek words, ᾽Ιησοῦς Χριστος Θεοῦ υἰὸς σωτήρ, which mean, “Jesus Christ the Son of God, the Saviour,” they will make the word ἰχδὺς, that is, “fish,” in which word Christ is mystically understood, because He was able to live, that is, to exist, without sin in the abyss of this mortality as in the depth of waters.

For the symbolic meaning of fishes and the "fish symbol", you could ask:

• Why are fish in general a Christian symbol?
• What is the historical significance/origin of the fish symbol called "ΙΧΘΥΣ"?
• Why is the fish often used as a symbol of Christ?