Fiddle小提琴，和 violin 是一个意思。 Play second fiddle 本意是“当第二小提琴手”，后来就引申为“担任副手；第二把手”。

【例句】
Being a modest person, he was content to play second fiddle to others.
作为一个谦虚者，他愿意居于他人的次要位置。

Tired of playing second fiddle, she resigned and started her own company.
厌倦了充当配角，她辞职并创办了自己的公司。