"Salad days" is an idiomatic expression, referring to a youthful time, accompanied by the inexperience, enthusiasm, idealism, innocence, or indiscretion that one associates with a young person. More modern use, especially in the United States, refers to a person's heyday when somebody was at the peak of their abilities—not necessarily in that person's youth.
The phrase was coined in Shakespeare's Antony and Cleopatra in 1606. In the speech at the end of Act One in which Cleopatra is regretting her youthful dalliances with Julius Caesar, she says: “...My salad days, / When I was green in judgment, cold in blood...”
The phrase became popular only from the middle of the 19th century, coming to mean “a period of youthful inexperience or indiscretion." The metaphor comes from Cleopatra's use of the word 'green' — presumably meaning someone youthful, inexperienced, or immature. Her references to "green in judgment" and "cold in blood" both suggest qualities of salads.
这个短语在19世纪中叶开始广泛使用，用来指代“年轻没经验或行事莽撞的时期”。这个比喻大概来自于克利奥帕格拉对green一词的使用，green(绿色)指年少、缺少经验或不成熟的年轻人，而green in judgment和cold in blood都显示了沙拉的特点。