That's why I thought the word could be from Tamil and tried to find out the meaning. But the word, as far as I could find out, doesn't exist even in Tamil. I know it does not exist in Hindi and don't think it might in Telugu.
So, as far as I know, Arima hardly has a meaning. Still, if you go a bit wild in searching and take into account more languages, you might find that Arima means Hill in Trinidad and Tobago where Arima is also the name of a town.
Most probably the word has been kept with the same meaning in mind as the sentence just before Arima Arima says 'ye hai yaantrik manav sabse ooncha' (this is the tallest machinic human, or robot).
So in my opinion, Arima means a hill. Any further details/suggestions are welcome.
Update: Arima is an old Tamil Word which means Lion. (Courtesy Hari)