In modern English usage, the noun hallow appears mostly in compounds in
Halloween and
Hallowmas. Halloween (or Hallowe'en) is a shortened form of All Hallow Even, meaning "All Hallows' Eve" or "All Saints' Eve". Hallowmas, the day after Halloween, is shortened from Hallows' mass, and is also known as "
All Hallows' Day" or "
All Saints' Day".
Hallows can refer to
saints, the
relics (including remains) of the saints, the relics of
gods, or
shrines in which relics are kept. Since the essence of these saints or gods were often considered present at their shrines and in their relics, hallows came to refer to the saints or gods themselves, rather than just their relics or shrines. Because of these various usage possibilities, the hallowed (sacred) hallows (relics) of a hallowed (holy) hallow (saint) might be hallowed (venerated) in a hallowed (consecrated) hallow (shrine).
^ Hah. All of the sudden, a "deathly hallow" has become even more cryptic than I had originally imagined.