To strike with sudden fear, terror, or wonder; to amaze; to surprise greatly, as with something unaccountable; to confound with some sudden emotion or passion
If something or someone astonishes you, they surprise you very much. Her dedication constantly astonishes me. = amaze. to surprise someone very much = amaze (astone (14-17 centuries) (from estoner, from extonare, from tonare ) + -ish (as in abolish))