Stu Dent kept pestering his classmate Ima Purfact as he wanted to copy her Algebra II homework assignment. Ima hesitated...because she thought it was wrong and also because Ima did not want their teacher to sanction her for aiding and abetting.
Stu tried to belay her fears: "Nobody will be able to trace my homework to you: I'll be changing the names of all the constants and variables: a to b, x to y, and so on."
Not quite convinced, but eager to be left alone, Ima handed her completed Algebra II assignment to Stu for copying.
After the homework was turned in and collected, Ima asked Stu: "Did you really change the names of all the variables?"
"Sure!" Stu replied. "When you called a function f, I called it g; when you called a variable x, I renamed it to y; and when you were writing about the log of x+1, I called it the timber of x+1..."