The symbol's use among Christians had become popular by the late 2nd century. In early Christian history, the ichthys symbol held "the most sacred significance." It has been claimed that Christians used it to recognize churches and other believers during a time when they faced persecution in the Roman Empire. A shibboleth to determine if another was indeed Christian. Some additional info on the history of the symbol. ἸΧΘΥΣ (IKhThUS), or also ἸΧΘΥϹ with a lunate sigma, is an acronym or acrostic for "Ἰησοῦς Χρῑστός Θεοῦ Υἱός Σωτήρ", Iēsoûs Khrīstós, Theoû Huiós, Sōtḗr; contemporary Koine, which translates into English as 'Jesus Christ, God's Son, Savior'. The symbol is about 9" long and 4" tall. It's carved from 1/2" MDF and finished in several coats polyurethane.