As a non-native English speaker I never connected SVN's trunk with the concept of a tree from which branches grow. I mean, I knew of this meaning of the word trunk but I never thought of it in this context. I was more familiar with the other meanings, the long body part on the elephant and the storage compartment on a car.
For some reason I'd associated it with trunk, a word for the human torso.
My guess is because "Main" was used in Microsoft's TFS.
It's just like some politicians - destroying anything the predecessor created, no matter how good it is.