fysin is the word used in the first image, fysis in the second. So what is being translated as nature shares semantic roots with the word "physics", with the physical. Maybe "the body" or even "the flesh" could sometimes replace this translation? Another translation might be "matter".
As to your Venus reference, notice that "mater" (mother) shares semantic roots with matter. In Spanish, matter is "materia". I think in Lucretius' Latin tongue this shared semantic history would have been much more evident.