What is "nighties"

Usage examples of "nighties".

Then he pulled the wad of nighties and blanket out of the crack and got the door shut.

She slept in flimsy, low-cut nighties because she knew he liked it, though in the winter she put an extra blanket on her side of the bed because she felt the cold.

She’d never mentioned the fact that he’d failed to return her nighties and her step-ins.