D defs.my
Entry 2 senses Webster, 1913

Erst

/(ẽrst)/ · IPA /ɝst/
01 adv. First.
  1. 1.
    First.[Archaic]
  2. 2.
    Previously; before; formerly; heretofore.
    “Tityrus, with whose style he had erst disclaimed all ambition to match his pastoral pipe.” — A. W. Ward.
Phrases & compounds
At erst — at first; at the beginning.
Now at erst — at this present time.