It is one of the Holly Ferns, Cyrtomium falcatum, likely the cultivar 'Rochfordianum', which is the one most propagaters produce.
Many sources rate it as a tender species and recommend using it only as a house plant. However, when planted in the garden, it is hardy, at least, to 0F (-18C) and one GW member reports it as hardy in Southern Ontario (Z6b). It has escaped cultivation and has become naturalized as far north as Ohio and Western NY, certainly beyond Z7. The site linked below, rates them hardy to Z6.
I have grown them in the garden for a number of years and while not evergreen there, produces new foliage in late spring. During the recent mild winters, have grown them in pots outdoors. As long as the roots remain moist, they will thrive, but as you are aware, increase very slowly.
Rb

Note: Sometimes the link works, other times it will redirect you to the index page, where you will need to click on plant names to proceed.

Here is a link that might be useful: Cyrtomium falcatum

Razorback 33, Thank you so much for your very complete answer! I definitely am going to put it in the garden, in a sheltered shady place. I don't remember ever having 0 degrees here in the DC area, and the winters now are much milder than ten years ago. I will mulch it well, and hope it will be happy. Thanks again.