Update April 26, 2019: according to my friend there is a Mustchup sauce already; it’s not known by that name.
In looking on Facebook this week, somebody posted a photo of Mayochup – https://www.walmart.com/search/?query=mayochup&cat_id=0&typeahead=mayochup (not an affiliate link).
It got me to thinking about other possibilities like Mustchup (mustard/ketchup) or maybe it’s Ketstard; how about Mayostard (mayonnaise/mustard) or Musonnaisse. Depending on the item, there are some foods I use both mustard and ketchup (hamburgers, hot dogs, etc.), but there are other things I only use ketchup (fries) or mustard (ham sandwiches) where I wouldn’t want to use Mustchup.
I am not a fan of mayonnaise or its cousin the non-mayonnaise alternatives – https://www.realsimple.com/food-recipes/shopping-storing/food/miracle-whip-mayonnaise.
Why Miracle Whip isn’t mayo: The U.S. Food and Drug Administration requires that anything labeled “mayonnaise” contain a minimum of 65 percent vegetable oil by weight. And though Kraft keeps Miracle Whip’s exact oil content a secret, the company confirms that it is too low to meet the mayo standard.
What makes it different: While it contains mayo’s key ingredients (egg, soybean oil, vinegar, water), Miracle Whip sets itself apart with a sweet, spicy flavor that some folks prefer. First introduced during the Depression, when its cheaper price made it alluring to people who couldn’t afford more highfalutin mayo, it’s now caught up, costing about the same amount per ounce as the real thing. At any price, Miracle Whip still has legions of devotees: According to Kraft, it’s currently among the grocery industry’s 20 top-selling brands.