Butthook, or Hook For Short is a Synonym to Butthead, Butthole, etc. Also can mean someone who is lazy. Bum

When you eat dirt for the first time and leave your family to build a shack in the woods

When you stick your finger up your butt and you get shit on it and then you stick that finger in your friend's mouth and pull really hard.

An attachment to the stock of a rifle or shotgun, often used in competition, which is tucked under the shooter's arm thereby counteracting the tendency of the weapon's muzzle to droop, or to allow one-handed firing.

1.
Known as a synonym to butthead, or bum. Short Form known as simply "hook".

a real jerk

A specific instance of a doohickey, considered to be the ultimate "useless thing".