This made me smile because this word means "those who burn" in one of the Bantu languages. :)
Well, not exactly the same but close:
apishi = burners (people who burn sth) Ndau
vapisi = burners (people who burn sth) Shona
What is more interesting is that Swahili chose to use a different word from the verb infinitive "to cook" , which is "kupika" All the Bantu languages I know derive the noun "cook" from the infinitive verb "to cook" .
A few examples:
Infinitive: kubika = to cook , noun: mubiki/abiki = cook/cooks --- Ndau
Infinitive: ukupheka = to cook , noun: umpheki/abapheki = cook/cooks --- Ndebele
Infinitive: kuapeha = to cook , noun: muapehi/baapehi = cook/cooks --- Lozi
It actually is the same - it took me my teacher pointing it out, it seems like a stretch, but :) : There is a causative form, which often/usually is -ish- (before the last -a of the verb). For verbs that end in -ka the k is dropped and turns into the sh.
Ah, but it seems much more fun to see it as connected to burning! Maybe when I lose concentration when cooking I can see it as improving my Swahili...?!