The hard drive click of death became a common term in the 1990's when a hard drive would make a clicking sound that was not normal and would mean that the hard drive was failing or is failing.
The hard drive click of death kind of sounds like someone pounding in a metal T Post with a T Post tool.
Click this link to hear a sound of a hard drive that is experiencing the click of death
https://en.wikipedia.org/wiki/File:WD_bad_heads_click_of_death.ogg
When that click of death happens you need a new hard drive and you should have your important data backed up before the hard drive actually fails.