This is the 3649th most frequent Japanese word.
驚かさ
"驚かさ" is a conjugated form of the verb "驚かす," meaning "to surprise" or "to startle."
Here, '驚かさ' is used as part of the verb '驚かされる', in passive form, indicating that the speaker was surprised by the movie.
その映画はとても驚かされた。
That movie surprised me greatly.
The word '驚かさ' is used in the imperative form '驚かさないで', suggesting an action to avoid causing surprise.
彼の秘密を聞いて友達を驚かさないでください。
Please do not surprise your friends by revealing his secret.
Here, '驚かさ' is part of the causative form '驚かさせる', used to indicate someone causing another to feel surprised.