According to Daniel Harms, in this spell, "falling away" refers to withering away.
From The Long Lost Friend:
A remedy to be used when anyone is falling away, and which has cured many persons.--Let the person in perfect soberness and without having conversed with anyone, catch rain in a pot, before sunrise; boil on egg in this; bore three small holes in this egg with a needle, and carry it to an ant-hill made by big ants; and that person will feel relieved as soon as the egg is devoured.
The grimoire The Long Lost Friend lists this spell.
Timeline of related events
1820Publication of Hohmann's Long Lost Friend (lists this spell)