CPU manufacturers often architect the structure of CPU units. CPU units include the structure of CPU die, heat spreader, CPU fan and so on. The structure of CPU is very important factor for long time use because it often determines how heats can be sent out of the structure for cooling them down.
Intel Ivy Bridge CPUs were notorious for this mis-architecture. There was slight gap between CPU die and heat spreader, heat was circulated inside not to be sent out, CPU temperature often reached to higher than usual.
So, there was idea to fill the gap with compound, which reduced some degrees of temperature inside. It was necessary task, users should open the head spreader taken off from the CPU structure, it is so-called 뚜따.
뚜따’s 뚜 is abbreviation of 뚜겅, 따 is 따기 which means all together as 뚜껑따기. Heat spreader covered on CPU die, it is figurative speech 뚜껑, and removement of it is 따기.
Intel has improved their design, so it is known as no longer users should do it.