Ichthus
ΙΧΘΥΣ is Greek for fish. It is an acronym for Ίησοῦς Jesus Χριστός Christ Θεοῦ God’s Υἱός Son Σωτήρ Saviour (Iēsous Christos, Theou Huios, Sōtēr) The letters can be combined to form a spoked wheel, as in this image at Ephesus: In the days that Christianity was illegal, and you wanted to check if someone