In ancient times there were Gauls on both sides of the Alps. The Romans called the area where they lived in Northern Italy "Cisalpine Gaul" while the area where they lived on the far side of the Alps (modern France) was "Transalpine Gaul."
The Latin preposition cis means "on this side of." It is cognate with the English word "hither." Latin C often corresponds to English H (canis/hound, centum/hundred, cor/heart, etc.)