In a note on thesis 8 of his "Eleven Theses on Heidegger and on Technology", Thomas Sheehan disputes the translation of Ereignis as enowning.

Beiträge [Contributions] and later works make it clear that Ereignis is not an "event" in any usual sense of the term (i.e., Vorkommnis und Geschehnis: SD 21.27) and that what Heidegger meant by Ereignis is not primarily "appropriation" or "enowning." In the forthcoming GA 71 (Das Ereignis, 1941-42) Heidegger shows that the original etymon of Ereignis is not eigen ("own," parallel to the Latin proprium, from which derive "appropriation" and "enowning") but rather eräugen/ereugen, "bringing something out into view." Heidegger got much of this from Jacob and Wilhelm Grimm. More importantly, however, in GA 71 (section "Das Ereignis," sub-section "Er-eigen -- Er-eignen,"), Heidegger annotated the Grimm etymologies, thereby providing his own understanding of Ereignis.

That and what follows (Grimm brothers' text, plus Heidegger's annotations) is essentially the same as section 6 of Sheehan's A Paradigm Shift in Heidegger Research, so I won't repeat it here.

Heidegger also made the connection between Ereignis and seeing in The Principle of Identity, although it was dropped from the second translation to not distract from its translation as "appropriation." Enowning, event, appropriation, and more (Αγχιβασιη?), all have their place in explaining what Heidegger is trying to convey. As Sheehan says:

Nonetheless, this is not to entirely exclude "appropriation" as a possible translation of Ereignis. That word might work -- but only if we understand the proprium of appropriation as the opening up of openness.

The key take away is that Ereignis is not a thing.

When Dasein properly takes up its thrown projection, the "there", or "here") opens up. Ereignis is "the appropriating event of the grounding of the there."

P. 87

das Ereignis der Dagrundung (GA 65, P. 247)

Ereignis connects things to Dasein, not in a relational way, but by gathering them together.  ¶ 6:53 PM