Lifting can cause it, but in my own experience, genetics play a key role. My dad had a stomach/ab wall hernia lifting a car door on a car he was rebuilding. My brother picked up a 20 pound box of someting and got the testicle hernia. My neice was born with a tear in her ab wall, with the intestine poking through. At age 6, the docs haev finally accepeted it won't be healing on its own, and she'll have surgery this week on it.
I've never had one, but I've had a few small crimps in the midsection that hurt for days. Never been injured anywhere else... just lots of aches and tweaks from the ab wall. No hernias yet, knock on wood.