Old English

Prefix

mōnaþ-

1. of or relating to the moon, lunar

   mōnaþfylen "the full moon, time of the full-moon"

2. monthly; lasting a month's time

   mōnaþādl "monthly illness"

   mōnaþbōt "penance lasting for a month"

3. denoting lunacy

   mōnaþsēocnes "lunacy"