Which is the correct usage: "rack my brain" or "wrack my brain"? Google turned up pages with conflicting recommendations.

[One argument](http://www.dailywritingtips.com/wracking-or-racking-your-brain/) is that to "rack a brain" comes from the [torture device known as a rack](http://en.wikipedia.org/wiki/Rack_%28torture%29).

Another from the now obsolete Yahoo Answers website was that wrack means damage or destruction or punishment and thus is correct.

Since I'm a SE user I'm inclined to immediately discount the second opinion from Yahoo Answers, but the logic seems plausible enough that I wanted to be sure.

On a related note, if *rack* is indeed correct, does the song [*Wrack My Brain* by Ringo Starr](http://en.wikipedia.org/wiki/Stop_and_Smell_the_Roses) simply have an ungrammatical title or is the error intentional?