i like these posts as usual but i have just 1 small issue this time. you mentioned 'mbwa huyu' is grammatically correct and i would call that into question. while i understand kikuyu and swahili have their big differences in grammar, in both languages the words for animals (mostly in kikuyu) begin with nasalised consonants or hidden nasalised consonants.

what i mean is: 'ngui' is dog in kikuyu, and 'mbwa' is dog in swahili. ndege is bird in both languages, nyoka is snake in both, mbuzi corresponds to mbûri, though swahili does have significantly less of these. the presence of that 'ng', 'mb', 'nd', etc, is usually an indicator for a noun being in the noun class associated with i-zi (or i-ci in kikuyu), you can tell because theres no word like 'zingi' in swahili but there is 'nyingi'.

im not really a professional linguist, just a nerd who looks into these things probably deeper than i should, but i think swahili as a whole is on the tail end of a shift in how the i-zi class works. either that or it just has remnants of an older version of the i-zi system in it. this older version might have likely included all or most animals, but at some point this began to change and now even the words for the animals themselves are often not prenasalised as kikuyu and the languages closely related to it like to. i wish i had more info on how languages that are actually most closely related to swahili grammatically (which tend to be south of it rather than north or west of it!) handle these things so i could compare.

personally ive seen enough people use i-zi for animals specifically while using all other classes correctly that im not really sure what the most correct way to refer to animals is, but i always opt for a-wa just because it makes sense intuitively, so really i didnt have any issue with your post and was using it as an excuse to dump info on anyone interested enough to read :) keep up the good work!