Possible Clues:

• Are shortly in the tree behind the barrel
• Are, in short, in the tree behind the barrel of the gun
• Awkward delivery bowled on repeat, endlessly
• Opening in gun
• Rear part of rifle
• Bottom-first birth position
• Bottom-first kind of birth
• Part of cannon leader of Roundheads found in tree
• Kind of birth with a rear-first delivery
• Drunk beer from Switzerland that might blow your head off?