Winter fern is a common name for Polystichum acrostichoides, a species of fern native to North America. This fern is known by several other common names that are synonymous with winter fern, including Christmas fern, sword fern, and holly fern. These names are all derived from the fern's evergreen nature, with its fronds remaining green throughout the winter months. Other synonyms for winter fern include rock fern, resurrection fern, and shield fern. Overall, there are many common names that can be used for this hardy and attractive fern, making it a popular choice for gardens, landscapes, and decorative displays.