before you can say Jack Robinson

Idioms and Phrases

Also, quicker than you can say Jack Robinson . Almost immediately, very soon, as in I'll finish this book before you can say Jack Robinson . This expression originated in the 1700s, but the identity of Jack Robinson has been lost. Grose's Classical Dictionary (1785) said he was a man who paid such brief visits to acquaintances that there was scarcely time to announce his arrival before he had departed, but it gives no further documentation. A newer version is before you know it , meaning so soon that you don't have time to become aware of it (as in He'll be gone before you know it ).