在18世紀的時候，這首兒歌其實是個謎語，謎底就是「蛋」。可是到了後來，

在18世紀的時候，這首兒歌其實是個謎語，謎底就是「蛋」。可是到了後來，謎底人人皆知，就沒有人把它當作謎語來看了，變成了一首普通的兒歌。

結果 (英文) 1:

In the 18th century, this children's song was actually a riddle, and the answer was "egg". But later, when everyone knew the answer to the riddle, no one regarded it as a riddle, and it became an ordinary children's song.

結果 (英文) 2:

In the 18th century, this nursery rhyme was actually a riddle, with the answer being 'egg'. But later on, the answer to the riddle became well-known, and no one looked at it as a riddle, turning it into an ordinary nursery rhyme.

結果 (英文) 3:

In the 18th century, this nursery rhyme was actually a riddle, and the answer was "egg". But later, when the answer was known to everyone, no one regarded it as a riddle and turned it into an ordinary children's song.