One of the notes in the classical paper LAMBDA: The Ultimate Imperative says:
The technique of repeatedly modifying a variable passed call-by-name in order to produce side effects on another call-by-name parameter is commonly known as Jensen's device, particularly in the case where call-by-name parameters are j and a[j]. We cannot find any reference to Jensen or who he was, and offer a reward for any information leading to the identification, arrest, and conviction of said Jensen.
Today, after almost 40 years since the memo was published, do we know the identity of Jensen? I'm not hoping for the reward, just curious.