Guadalcanal is not a canal, although its name comes partly from the Latin word "canalia", meaning "a canal" or "waterpipe". But Guadalcanal is actually a volcanic island, the largest of the Solomon Islands in the Pacific Ocean. Did your father or grandfather fight in World War II, and possibly you were named after the famous battle of Guadalcanal?
Here is a website, which will give you the origin and meaning of the name of that island:
http://www1.elpais.es/andalucia/uk/pueblos/118a_guadalcanal.htm
-- Nanaea