The dialect here is pidgin-English. A pidgin language is a grammatically simplified way of communicating between two groups, in this case, Chinese dock-workers and European sailors. In this song, the Chinese words come from Cantonese. The intent here was not to belittle someone's language skills.
The song probably originates in the days of the tea clippers, when the Canton River and other ports such as the Golden Pagoda anchorage, Foochow-fu, were full of ships loading tea. Stan Hugill learned it from Capt. Sternvall, presumably from his 1935 book Sång under Segel.