In Norse mythology
(“battle swine”) was Freyja's boar
which she rode when not using her cat-drawn chariot
It was also the helmet of Áli that was taken by the Swedish king Adils after the Battle on the Ice of Lake Vänern that ended with Áli's death.
In Beowulf, it is said that a boar on the helmet was there to guard the life of the warrior wearing it.