Object3D pivot/axis position

As above - they are always drawn at object’s world-space position (which is equivalent to object’s local (0.0, 0.0, 0.0) position.) The location of that (0.0, 0.0, 0.0) point depends on the model itself - if you import the model in Blender and select it, this point will be marked with an orange dot:

(Here and here to be more precise.)

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(You can modify that point in Blender by pressing Tab, and moving the vertices around - that way you’ll shift the pivoting point into the opposite direction.)