This sugests that it is a variant of 'eat someone alive':
Student or Learner
seeking the negative connotation for this idion
I think it means to do everything for someone.Originally Posted by MW
Having cooked a meal you might say 'I suppose you want me to eat it for you?'
This comes from the movie Wall Street
Remember your school bully who would eat your lunch?
I think it means take away something from you.
In the Wall Street context, it would appear to mean 'take from'.
In the Wall Street context, it's a threat that legally doesn't imply exact consequences (thus not necessarily physical). Remember...
GEKKO (on phone)
... what the hell is going on? I
just saw 200,000 shares move, are
we part of it? We better be, pal,
or I'm gonna eat your lunch for
you... get on 1.
The real message here, however, is a death threat, albeit exagerated. He won't need to eat his lunch when he's dead, so Gekko's going to eat it for him.
Or maybe its been misquoted:
'Eat you for lunch" would be a threat
"Eat your lunch for you" more like a sarcastic expression implying you can't even do that for yourself