Frank Duckett was an American running a shrimp stand in Australia. Sawyer was told by his associate Hibbs that Duckett was the original Sawyer. However, it turned out that Hibbs had tricked Sawyer, and Duckett merely owed Hibbs money, and because of this, Hibbs wanted Duckett dead, and thus Sawyer was conned into killing him. Just before he died, Duckett told Sawyer, "It'll come back around." ("Outlaws")
As Sawyer is walking through the jungle in "Outlaws", whispers are heard of Frank Duckett and another unknown voice. Duckett says, "It'll come back around." (Whisper transcripts).
Australians actually call shrimp "prawns." The widely-held perception of "tossing a shrimp on the barbie" dates back to Australian tourism advertisements of the 1980s, which deliberately used the term "shrimp" because they were aimed at foreign audiences.