1340,
astonien, from O.Fr.
estoner "to stun," from V.L.
*extonare, from L.
ex- "out" +
tonare "to thunder" (see
thunder); so, lit. "to leave someone thunderstruck." The modern form (infl. by Eng. verbs in
-ish, e.g.
distinguish, diminish) is attested from c.1530.