The difference between "astonish" and "surprise"
France's greatest lexicographer, Emile Littré, was once found by his wife, in flagrante, and in the conjugal bedroom at that, with their housemaid. Happily, the exchange that followed makes sense almost as well in English as in French.

"Emile," cried Mrs Littré, "I am surprised!"
"No, my dear," replied the erring lexicographer calmly. "You are astonished. It is we who are surprised. "

It occurred to me that I did not know etymology of "astonish"
From AHD
astonish

SYLLABICATION: aˇstonˇish
PRONUNCIATION: -stnsh
TRANSITIVE VERB: Inflected forms: asˇtonˇished, asˇtonˇishˇing, asˇtonˇishˇes
To fill with sudden wonder or amazement. See synonyms at surprise.
ETYMOLOGY: Alteration of Middle English astonen, from Old French estoner, from Vulgar Latin *extonre : Latin ex-, ex- + Latin tonre, to thunder; see (s)ten- in Appendix I.