I've seen many examples like this one about how to do per-module translations. It looks like this:
"Product Name","Items in Your Cart"
"Mage_Checkout::Product Name","Items in Your Cart"
However, in all of the versions of Magento I've tried it on, (18.104.22.168, 22.214.171.124 and 126.96.36.199) this doesn't work.
Is this for an outdated version of Magento, or am I doing something wrong?