The spelling is from middle English, where multiple spellings of a word based on phonemics were generally accepted. There are significantly more varieties of mylks that can be made or purchased in stores than there are varieties of milks from animals that humans consume.Using the word “mylk” also clearly distinguishes it from the common understanding of milk. It helps avoid misunderstanding when discussing vegan products and recipes, where the person wants to emphasize that it’s a plant derived product.In some locations, alternative spellings like these also help avoid lawsuits from vested interests (for example, Silk Soymilk was sued in the U.S. for using the word “milk” for a plant derived product; that lawsuit was later dismissed).Lastly, the word “mylk” also evokes curiosity in the reader and provides a chance for those who consume these mylks to explain to them about the countless alternatives available.
Person 2: This terrific cashew mylk smoothie with peanut butter and bananas.
Person 1: Can you tell me how to make cashew milk and almond milk?
Person 2: Yes, I can. But we call it “mylk” to distinguish it from animal milk.