From Jacques Taminaux's book on Arendt's intellectual relationship with Heidegger:

In the use Heidegger makes of [Ereignis], the word does not designate anything particular, nothing being, nothing plural, but merely the movement of appropriation that Being is and to which the thinker corresponds. That Ereignis thus understood as appropriating event--indicating that Being withdraws from all those ontic appearances to which it gives rise--exceeds every plurality and ultimately every sharing of words is something that Heidegger himself suggest when he writes in one of the densest texts on that theme: "What remains to be said? Only this: Appropriation (Ereignis) appropriates" [P. 24]. The fact that in the relationship to Ereignis thus understood what is at stake is less the dialogue of one with oneself(in which the thinking activity consists) than thaumazein (inasmuch as it extracts its speechless sign from every plurality) is something that Heidegger himself suggests when he connects Ereignis to what he calls Eraugnis, i.e., to a gaze that collects and gathers.

Ereignis, therefore, needs a seeing that corresponds to it intimately, just as in Being and Time Dasein's ownmost (eigentlich) can-be needed the twinkling of the eye, the Augenblick. One more bios theoretikos, or more precisely thaumazein, leads the speculative thinker to devour worldly events.

P. 197

Glossary:
thaumazein: Wonder; as in Socrates: "wonder belongs to the philosopher".
Eraugnis: Archaic spelling of Ereignis. I have only come across it in a translators' note in Zollikon Seminars.
bios theoretikos: the contemplative life, as opposed to bios politikos; see Aristotle's Ethica Nicomachea.  ¶ 8:08 PM