"There is a crack"
Oh, is this maybe related to the nipo nimo niko stuff?
I always read in books that there are specific differences for those, like nimo would be in a vein similar to how you described mma. My tanzanian fiancee says that it might really be that nipo nimo and niko mean different things but that the reality is that everyone shes knows in tanzania just picks one and always uses it for all purposes. Please excuse the tangent. :-P
Pretty much. The Mahali noun classes (pa, ku and m) cover different degrees of placement.
Ku is the vaguest. Think of niko as "I am roughly in this area". Uko wapi? Niko kijijini. "Where are you?" "I'm in the village".
Pa is more specific. Think of nipo as "I am here at this location". Uko wapi? Nipo nyumbani. "Where are you?" "I'm at home".
M is more specific still. Think of nimo as " I am right here, inside an enclosed space". uko wapi? Nimo jikoni. "Where are you?" "I'm in the kitchen".
This is, obviously, a rather simple explanation and it is a little bit more nuanced than that. It does seem though that the distinctions may be on their way to obsolescence.