"Sie bawten einen tempel gross darein zu eren[in honour of] Zise der abgoettin, die sie nach heidnischen sitten[after heathen ways] anbetten zu denselben zeiten[adored in those days]. Die stat ward genennt[city got named] auch Zisaris nach der abgoettin[after the goddess], das was der pris. Der tempel als lang stund unversert[stood uninjured], bis im von alter abgieng[as from age it passed away], der berg namen von im empfieng[the hill took name], daruf gestanden was[whereon had stood] das werck, und haist noch huet[hight still to-day] der Zisenberck."
Grimm says that the older spelling of Her name is Cisa and "that she was most devoutly worshipped by the Suevi" and Her great feast day which consisted of games and merrymaking was held on 28th September. Grimm speculates that Zisa/Cisa is the same divinity as Isis who is referred to in Tacitus` Germania 9.1: "Part of the Suebi sacrifice also to Isis; I have not ascertained the source from which the foreign rite originates, but the fact remains that the image itself, fashioned in the form of a light ship, proves that the cult is imported." It is more than likely that this Goddess was not foreign or imported but really another case of Tacitus ascribing a Roman name to a local Germanic deity which he does to other deities in his work. Rudolf Simek in his Dictionary of Northern Mythology suggests a link with the West Germanic Goddess Nerthus and the Frisian Nehalennia because of the association with the ship.
Nigel Pennick[The Complete Illustrated Guide to Runes] identifies Zisa as the consort of the God Ziu/Tyr/Tiu/*Tiwaz. Could there be an association between Zisa/Cisa as the rather even more obscure German Goddess Isa? The name would suggest it. Indeed when one considers the form of the Tiwaz and Isa runes there certainly does appear to be a link on various levels. Thus far I can only find a few references to Her: "[Rassmann identifies Island as derived from Isa, a goddess of the under-world, probably the same as Holda, and not as Iceland]."[Jessie L. Weston, Legends of the Wagner Drama].
Wilhelm Waegner in his Asgard and the Gods also refers to this mysterious Goddess:
"Nehalennia, the protectress of ships and trade, was worshipped by the Keltic and Teutonic races in a sacred grove on the island of Walcheren; she had also altars and holy places dedicated to her at Nivelles. The worship of Isa or Eisen, who was identical with Nehalennia, was even older and more wide-spread throughout Germany. St Gertrude took her place in Christian times, and her name[Geer, ie spear, and Trude, daughter of Thor] betrays its heathen origin."
Nicholas Goodrick-Clarke in The Occult Roots of Nazism. Secret Aryan Cults and Their Influence on Nazi Ideology refers to a mention of Isa in one of the works of Guido von List: "The town of Ybbs was, according to List, founded upon a shrine to the Teutonic goddess Isa;...." The work which Goodrick-Clarke refers to is Deutsch-Mythologische Landschaftsbilder. My readers will appreciate that whilst the Norse Eddas give abundant information about the principal deities of the Germanic peoples, especially in Scandinavia they are a poor resource for information about the continental Germanic or Anglo-Saxon peoples so we must use sources other than these for information about German Gods and Goddesses.
Waegner refers to the antiquity of Isa. In my studies over the years I have come to realise that the older any deity is the least we know about them. A case in point is Tyr/Tiw/*Tiwaz, a God regarded as being much older than Woden and cognate with the Indo-European Sky Father *Dyeus. He is commemorated in the name of the third day of the week Tuesday in various Germanic languages. The Eddas seem to relegate Him to a role inferior to that of Woden but this was not always the case. The rune Tiwaz of course also is named after Him. So the scarcity of source material is no indication of the former importance of any deity. I have not yet obtained a copy of August Rassmann`s work but intend to do so in the near future.
The above-mentioned two references to Isa identify Her as a Goddess of the underworld and She is associated with ships. We must remember that in the Germanic world there have been many discoveries of ship burials and clearly our ancestors drew a link between the ship and the underworld. Likewise Isis is associated with both water and the underworld. We also recall the descent of the Goddess Ischtar into the underworld and the more recent revelations concerning Isais[Goddess who resides in the Untersberg] and her descent into the underworld to recover the black stone[the graal]. Prudence Jones and Nigel Pennick[A History of Pagan Europe] speculate that the Istaevones could have been named after the river Histar or Istar, the original name of the Danube or Donau and Ista could have been the deity of the river. We know that generally in territories formerly occupied by the Celts that the rivers were associated usually with Goddesses rather than Gods which supposes again the deity Ista and the link with Isa. Apart from Nehalennia the astute reader will notice that the Goddesses Zisa, Isa, Isais and Isis were all worshipped in the area of Bavaria and Austria which makes a link between all or most of them much more tenable on geographical as well as linguistic and mythological grounds.