Translation:They are drunk
I want to parse "wamelewa" as "they have been eaten". So I have two questions:
I get "wa" = "they" and "me" = immediate past, so presumably "-lewa" is something like "become drunk". But is there a different literal meaning to "-lewa" at all? Like how in English the word "drunk" is the past participle of "drink" - "I have drunk the milk". And you would say "he is drunk" and "he is A drunk" and they're both derived (presumably) from the concept of drinking alcohol, because the alcohol is implied (c.f. "I could do with a drink"). So does "-lewa" have a similar interesting derivation?
How would you actually say "They have been eaten"?
Yes, the causative verb is kulevya i.e. 'to intoxicate'. A drunk (n) is "mlevi" (alcoholism/drunkenness is "ulevi"). 'kulewa' (to get drunk/intoxicated) is the passive form of 'kulevya'. As an aside (and purely coincidental), 'lewa' can also mean 'to be raised/reared' (as in a child by a parent) e.g. Alilewa na babu yake - '(S)he was raised by her/his grandfather'. Comes from the verb stem 'kulea' (to rear/nurture)
"they have been eaten" would be "wameliwa" OR "wamekulwa". The monosyllabic verbs tend to have interesting derivatives