Be not terrified (μη πτοηθητε). First aorist passive subjunctive with μη from πτοεω an old verb to terrify, from πτοα, terror. In the N.T. only here and Luke 24:37.

First (Πρωτον). It is so easy to forget this and to insist that the end is "immediately" in spite of Christ's explicit denial here. See Matthew 24:4-42; Mark 13:1-37 for discussion of details for Luke 21:8-36, the great eschatological discourse of Jesus