Today I learned that the term "Blue Card" was initially coined by Jakob von Weizsäcker, a German economist working for the Brussels-based think tank Bruegel. I just briefly checked and so far, the first time I could find the term in the context of EU-policy was indeed in a 2006 publication (PDF) by Bruegel.
Hearing the author personally today, he told that although the EU institutions have used the term he has been proposing, the final result of the directive is far away from the think tank's proposals, being much more restrictive than initially advised.
von Weizäcker stressed in particular that the
I am not an expert in this issue, but I have just seen that there is a specialised blog on the "Blue Card" policy process, so anyone interested in more details should check it out!