One very important code was never broken. It was used during World War fl by the Americans.
二战期间，美国的一种密码从未被敌方破译。
老爸老妈的浪漫史视频版（第五季）
You're gonna fl in love. - So soon.
你会坠入爱河 - 很快。
英语百科
Floruit
（重定向自Fl.）
Floruit (/ˈflɔərjᵿ.ɪt/ or /ˈflɒrᵿ.ɪt/), abbreviated fl. (or occasionally, flor.), in Latin meaning "he/she flourished", denotes a date or period during which a person was known to have been alive or active. In English, the word may also be used as a noun indicating the time when someone "flourished".