In literal terms, “strap” means a gun so “get the strap” would mean, “get the gun” but that is now how it's used in slang.

What's a strap in the military?

"Quite literally a strap is a member of the team attached or strapped to them in order to provide highly specialized language skills. ... A strap experiences the same mission dangers as the rest of the team but may actually be part of the advance team because they can speak the language fluently for the entire team."

What does the acronym strap mean in writing?

STRAP. Section, Township, Range, Area, and Parcel.