"Bayou", "gumbo", "lagniappe" and "Laissez les bon temps rouler" are common Cajun slang terms. Cajun slang features many words and phrases borrowed from the French language, as many French speakers from Nova Scotia moved down to Louisiana in the 1700s.
Although French features in New Orleans slang, many of New Orleans' residents speak little to no French. There are several spoken dialects across different areas of New Orleans.
A "bayou" is a stream that runs through marsh or swampland. "Gumbo" is a kind of soup that is based on a roux. It may contain chicken, duck, shrimp or other seafood. "Lagniappe" is something extra that was thrown in for free, or a pleasant surprise. "Laissez les bon temps rouler" is French for "let the good times roll," an upbeat phrase.