Terminology
Where is the term  "Red sauce" used?
Ketchup
The term used for the sauce varies. "Ketchup" (sometimes spelled "catsup" in American English, called "a failed attempt at Anglicization") is the dominant term in American English and Canadian English, with "catsup" being the prominent term in some southern US states. In these dialects, "tomato sauce" refers to pasta sauce, and is not a synonym for ketchup. "Tomato sauce" is more common in Commonwealth English (e.g., Australia, India, New Zealand and South Africa). In British English, the two terms are interchangeable. "Red sauce" is used in Welsh English, Scottish English, Irish English and some parts of England, such as the Black Country, and in South London, often contrasting with brown sauce with which it is often served but in Canadian and American English, "red sauce" refers to red spicy sauces (or sweet and sour sauce) and is not a synonym for ketchup. The etymology of the word "ketchup" is unclear, with multiple competing theories: