Terminology
The term used for the sauce varies. Ketchup (sometimes spelled catsup in American English) is the dominant term in American English and Canadian English. 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.
The etymology of the word ketchup is uncertain, with multiple competing theories:
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