The ICQUS

 
The Greek word ICQUS (ictuses) means “Fish” The early Christians would secretly use the symbol of the fish to let other Christians know that there were Christians in the city. They had to use symbols because it was illegal to be a Christian. They chose ICQUS or the Fish because the word ICQUS also formed an acrostic for Jesus Christ God, Son, Savior. 
I
stands for
IHSOUS
Jesus
C
stands for
CRISTOS
Christ
Q
stands for
QEOZ
God
“Y”
stands for
UIOE
Son
S
stands for
SOTHR
Savior
 The early also used the symbol of the wheel because it also formed the word ICQUS.