"I'm scared!" said Nora trembling, as she took hold of my arm.

took 是动词 take 的过去式，意思是"拿、取"。 hold 是名词，意思是"抓住、握住"。 of 是介词，表示所属关系或连接作用。 take hold of 是一个固定短语，意思是"抓住、握住"，表示用手紧紧抓住某物或某人。