This name makes no sense. The 3rd law of thermodynamics, paraphrased, is: as the temperature in a system drops, so does the level of entropy, such that at absolute zero, or zero degrees Kelvin, entropy will also be at zero.
This comic has a sentient, parasitic vinyl dragon suit and a shapeshifting actual dragon.
Well, I think the reason the name is "The 3rd Law of Thermodynamics" is because the creation of this comic has driven the universe a tiny bit closer to being a system of total zero entropy, just like every other action. Like eating a parasitic dragonthing and being devoured in turn by the parasite. Makes sense to... Someone, probably.
The Third Law of Thermodynamics has the consequence that all systems will ultimately trend toward entropy, and is often less accurately phrased in those terms when not speaking in a technical context. "Entropy" is also popularly associated with chaos and corruption. From that perspective, the title reflects the fact that corruption was the only possible outcome -- the corrupter was a suit and thus not traditionally killable, if she had let him go he would have just attacked her again later, and by eating him she still allowed him to corrupt her.
It... didn't take me too long to figure that out, TBH.
ETA: Also, when I looked it up to find if there was a different explanation at the source, I found that apparently the person it was a gift for says the corrupting dragon is also female?