Alu is a charm word appearing on numerous artifacts found in Central and Northern Europe dating from the Germanic Iron Age. The word is the most common of the early runic charm words and can appear either alone or as part of an apparent formula. The origin and meaning of the word are matters of dispute, though a general agreement exists among scholars that the word either represents amulet magic or is a metaphor (or metonym) for it.[4]
Source: Runic magic – Wikipedia
Tim B.
https://en.wikipedia.org/wiki/Alu_(runic)