In full "pyxie moss". A prostrate, mosslike evergreen shrub, Pyxidanthera barbulata (family Diapensiaceae), which bears numerous tiny white or pink flowers and is found in the pine barrens of New Jersey and the Carolinas.
Late 19th century; earliest use found in Harper's Magazine. Shortened from scientific Latin Pyxidanthera, genus name (A. MichauxFlora Boreali-Americana I. 152; from Hellenistic Greek πυξίδιον small box + ancient Greek ἀνθηρά, feminine of ἀνθηρός flowery).