Pirate cant

From AJS.COM

The pirate cant is an ancient pidgin, evolved from the Common trade tongue, the Keolandish (or "Keoish", for technical sailing terms and navigation) and a smattering of other sources. To make it more confusing (by design and for the convinience of the users), words foreign to Common are often permuted into their closest equivalent. For example, the word "cagia", which is Suloise for "magic device" has been absorbed by the cant, but is usually spoken as "cake". Place names and words refering to illegal activities are almost always replaced to disguise the topic of conversation. Conventions on these replacements are regional, but some norms exist along all major trade routes.

Use

Most of the rest of the structure is the same, and a native speaker of common can often understand most of what is being said in the pirate cant, though not the specifics. While the pidgin is called "pirate cant", it is often spoken by legitimate traders as a sort of "sea common" where Keoish is not widely known.