In the old language “km.t” was feminine. But, I have noticed this with some words, where the gender changes by the time of the Coptic language, so it’s not unusual to see this happening. You can see this change by the time of the Demotic Script being used because “km.t” is then spelled “kmy”. I’d equate this to the Ancient Egyptian language being a “regressive” language, in the sense that the words and grammar (unfortunately) were corrupted through time due to unstable politics affecting the society in those points of times between and during the various dynasties. These are signs of a living language dying, there were many Greek historians who literally wrote about the Egyptian language claiming that “the people were forgetting their own language”... and still to this day there are examples of languages that go through this “regression”, some languages that come to mind would be the Hawaiian language, and the Native American languages of the United States and in South America.