It was a battle cry of the tribes of Heiðmǫrk (todays Hedmark in Norway). The name of the place itself stems from Norways biggest lake in the country - Mjǫrs (Mjøsa) - (Heinernes sjø), and the fact that the Norse meaning of this place could be translated as "the land of the pagans".
The scholars can make no sense of this battle cry and have translated this litterally as "beer, beer, onion!" I quess you can see the warrior tribes of Heiðmǫrk before you - screaming "beer, beer, onion!" before they charged against the enemy - as it would be in a modern HBO series of Vikings dressed up like bikers, drunk on ale and high (dead sick) on mushrooms...
In other words, there is more to it than ale and unions.
The "word" alu is found extensively on rune stones in Scandinavia. In many cases only with the "word" alu. To find any meaning in this, we have to return to our "hidden wisdom" - the runes.
ᚨ*ansuR (áss)
Æsir.
Önd (spirit), breath (anda).
Life force.
Óðinn.
Galdr.
The ash tree.
The element air.
The planlet Pluto.
The realm of death.
Wolf.
Raven.
Eagle.
Horse.
Re-birth.
Order.
Consciousness.
Knowlegde.
Wisdom.
Creativity.
Reason.
ᛚ*laguR (logr)
Water.
Fluidity.
Life force.
The spark of life.
Life energy and growth.
Birth.
Dormant yeast of past lives (awakes between fire and ice - when structured water (ice) is released to fluid).
Logr - "sorcery" (Freya, the seed)).
The energies between life and death.
Njǫrðr.
Old Norwegian: Laukr.
The willow tree.
ᚢ*ūruR (úrr)
Wild bull.
Ox.
Auðhumbla/Ymír.
Ancestral power.
The birch tree.
The element water (ice).
Through Fehu´s fire - creation.
Primal forming force giving structure to the primal fire.
The forces of creation.
Structure.
Formation.
Inner strenght.
The "word" alu is composed of the runes áss, logr and úrr. That is no coincidence of "letters" giving a word. These three runes represent air, fire, water and soil. The components needed for anything to grow (be born, re-born). The rune úrr is thus related to not only ancestral power, the wild bull - but to the primordial Ettin Ýmír (the "beginning" of the eternal cycle), and is the metaphor for soil, Jörð - the burial mound - being the symbol of the micro cosmos in of itself.
The Elgsem rune stone from 400 CE.
Bracteate from Djupbrunns in Sweden from 400 CE.
Fibula from Værløse in Denmark from the 3rd century. The inscription is "alugod" and as the item above followed by the swastika (eternal cycle).
The proto-Nordic word laukaR is a word for onion, yes, but it is also a word for fertility - for anything that grows. Thus, it is the old Norwegian word for the rune laguR itself. The green gras of everything re-born after Ragnarök (the new beginning) in Vóluspá is named laukaR, and inside it searching - the honorable re-born will again find the golden tablets of ancestral memory reflecting Sól (the primordial fire), those they owned in times immemorial.
When we know all this, there is no coincidence that the archaeologists in Scandinavia have found items with these inscriptions from the burial mounds and graves, on several rune stones etc. There is no coincidence that the battle cry of the pagans was "alu, alu laukaR!" either.
You invoke your accumulated honorable ancestors, you invoke the honorable you, your courage, your deity of battle - Óðinn. You invoke and acknowlegde your eternal destiny, either victory or death - in the primordial struggle. You invoke your honor to walk in shapes and shadows, and be-reborn through the elements of the Gods - and to spring a new from the sun, on the stones as the green, fertile accuumlated laukaR of alu.