When ever two modules have same translate string, priority is given to current module first (if translation is called from current module files) and then it depends on which module loads first.
If you have two modules Mage_A and Mage_B, both have a translate string ‘Hello’.
This is how magento stores it internal
Mage_A::Hello => A1
Mage_B::Hello => A2
if we call
Mage::helper(‘A’)->__(‘Hello’) //this will print A1
Mage::helper(‘B’)->__(‘Hello’) //this will print A2
problem happens when we call the translate string from a third module e.g
during this time which every module loads first A or B, that string will be printed.