What is "bivvies"

Usage examples of "bivvies".

He could just have them disperse to the sides of the canyon in their bivvies, but he didn't like the looks of the weather.

Since he knew what he was looking for he could tell where the bivvies were.

In the semi-darkness he could make out, on all sides, lines of hobbled ponies, squatting camels, stacks of merchandise, and low bivvies under which porters and drivers were sleeping round dying fires.