After spending a few months over there, he got back to Switzerland, where he worked in a private bank as a trader in the bond market.

trader 是由动词 trade（交易）加上后缀 -er 构成的名词，表示"从事交易的人"，即"交易员"。在金融领域特指在市场上买卖证券、债券等金融产品的专业人员。