GIVE 'ER can apply to anything from jamming the throttle on your big block wide-open to you and the boys putting a bit of muscle into whatever misguided task you've drunkenly committed to.
GIVE 'ER can be applied to nearly any situation where finesse is no longer a viable option.
2. A form of permission.
3. A suggested course of action.
This will work if:
1. Terry is about to do something reckless and is being egged on by friends who are encouraging him to continue/begin this action regardless of the consequences.
2. Terry asks if he can get a beer from the fridge. (typically reduced to one "give'er" instead of the above multiple "give'er's"
3. Terry asks you if its a good idea to ask out that good looking woman he sees.
2. ... so then he says it's touching cloth and I says give 'er lad, no one'll know it was you......