John Macquarrie on the event of appropriation.
So this ultimate source is not a substance but an event, as indeed is clear from the name we have already learned, 'It gives'. But it is an event of 'appropriation'. What does that mean? The German verb ereignen usually means simply 'to happen', while the noun Ereignis is simply 'event'. But in using such words, Heidegger is again exploiting their etymology and drawing attention to relationships usually left unobserved, yet which lie deep in language and presumably in thinking. Ereignis includes the root eigen corresponding the the English word 'own'. This word eigen is, of course, also met in the word eigentlich, which we have translated 'authentic', as when we speak of an 'authentic existence'. The Ereignis then is just not any event, but the event of appropriation, when something is made someone's own. This appropriation would seem to be the other side of the act of giving. So we read: 'The gift of presence is the property of appropriating' [P. 22]. But almost immediately we are warned that sometimes instead of the granting of a presence there may be a withdrawal, and we shall see later what this means. But meantime we are concerned with presence and presencing rather than withdrawal. To what does Being present itself? Obviously to Dasein, the being who is a clearing, the locus where the light gets through, the one who has access to unconcealedness, to being in truth. The idea of an event of appropriation therefore gathers together many items in Heidegger's thinking.