Ichthys Cross
also known as Fisherman's Cross
A plain cross without lettering is one of the most common designs for necklaces, usually worn for decoration only. Adding the Greek ΙΧΘΥΣ (Ichthys) lettering reminds people of the Christian meaning of the Cross.
Ichthys is a Christogram or Chrismon, a monogram of Christ, and was in use by the 4th century if not earlier. The Greek spelling (ΙΧΘΥΣ) and how that becomes a Christogram is explained more on our Jesus Fish page.
Other Chrismons include INRI, Alpha and Omega, Chi-Rho, ICXC and IHS; all of which are more commonly seen with the cross than Ichthys.
Sean Wright noticed this neat variation of an Everlasting Cross on a magnet sold by CafePress (cafepress.com/+jesus-fish+magnets).
What is "Ichthys"?
Clemens was a Greek theologian and noted that letters of the Greek word for fish, ΙΧΘΥΣ (pronounced Ichthys), made the following neat little acrostic:
Ι (Iota) Ιησοῦς |
Χ (Chi) Χριστός |
Θ (Theta) Θεος |
Υ (Upsilon) Υἱός |
Σ (Sigma) Σωτήρ |
Iesous | Christos | Theou | Yios * | Soter |
Jesus | Christ | God's | Son | Saviour |
(* pronounced Iios) |
So in addition to the simple and easily recognisable symbol, there is also a motto that describes Jesus as Christ, God's Son, and Saviour.
This use of the fish might also have been partly a protest against the Pagan emperors of the time, who named themselves Theou Yios (God's sons), which appears on Alexandrian coins minted during of the reign of Domitian, 11th Emperor of the Roman Empire, 81-96 AD.
Source: Antiquities of the Christian Church, 3. Peculiarities of the Christian System.