There are even more versions:

Colombia
Columbia
Colón
Colombo
Columbus
Colomb
Colom

Places were usually named by settlers according to the rules of their own language. Columbus is the Latin variant, Colón is Spanish, Colombo Italian.

Back in 15th-16th century translating personal names was common. The practice is still continues with monarchs today, see popes - John Paul ll was also Iohannes Paulus, Juan Pablo, Ivan Pavao …