Origin of bob wire
An Americanism dating back to 1925–30; by folk etymology
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018
Examples from the Web for bob wire
He rolled under the bob-wire fence and started down between the com rows as hard as he could go.
The water had come up and covered it up to the tops of the bob-wire fence posts.