hoi means 'the'
polloi means 'people'
The hoi polloi means 'the the people'. It is tautological. You don't need the extra 'the'.
Sorry, but it grates on me. Yes, I do have more important things to do, but I am desperately trying to avoid doing them 
No, this is not aimed at anyone in particular, either here on in RL, but I have just heard yet another person using the phrase so I thought I'd disseminate the info as widely as poss.
Hound me, I probably deserve it