Incorrect spelling, explanation: turnk is incorrect because it strays from the Latin original word truncus, from which the current word, trunk was borrowed. Another reason is more intuitive, as the rnk is really difficult to pronounce, so it’s safe to assume such a consonant cluster would not function in English.

Correct spelling, explanation: trunk is a word borrowed from Latin truncus. As you can see, both forms are pretty similar: the word lost the specific Latin suffix -us, and c was changed to k because of the pronunciation, but other than that trunk is still pretty similar to its predecessor.

Definition of trunk:
noun
1. the woody, stem part of a tree
The trunk of the pine began to rot but the branches were still green and alive.
2. a human torso
I went to the doctor to diagnose the pain in the middle of my trunk.
3. elephant’s nose
We mostly associate the trunk with elephants, but anteaters also have trunks.
4. the large space in the rear end of a car designated to carry things
I put my shopping bags in the trunk, but they fell over and everything fell out.