Did you-all see this? I thought it was pretty cool.
From: Bill Moore (bill.mooreATwarnerbros.com)
Subject: Re: A.Word.A.Day--grip

I run the Grip Dept. at Warner Bros. Studio and I have one small correction to where the term "Grip" came from. Being a 3rd generation Grip (thank you, nepotism) my Grandfather passed on to me this history. Back in the 1920s, before IATSE unions were around, workers would stand in front of the studios waiting to be chosen for work, any work. The ones that were picked and then assigned to pick up the Actors' luggage at the train depot were called Grips.
Apparently luggage items were earlier were referred to as Grips and the name transferred to those assigned to that task. When the unions came into play and jobs were divided up the name Grip stuck. Not too glamorous but that's the story.