This is the past tense and third person of the verb 'Wariwa' 'to go away'. To create the past tense replace the present tense ending 'a' with the past tense ending 'in'. Depending on context this phrase could mean 'he, she or it went away.' (Note 'wariwa' and 'wariwin' has the pronunciation variation for the 'a'. It comes between 'w' and 'r' and is pronounced the same as the English 'war'.)