Malte
It is not your English or business educcation, is that the term used in the eLearning community was not well chosen. I think the origin is more from the humanities, for example artists normally keep portfolios.
IMS calls the relevant specification 'ePortfolio': http://www.imsglobal.org/ep/index.html
Some more info:
http://www.deskootenays.ca/wilton/eportfolios/whatitis.php
Other also called them webfolios:
http://www.elearnspace.org/Articles/eportfolios.htm
Competitors (i.e Sakai with http://www.theospi.org/)
called them portfolios so I think that is the only way to go.
cheers
Rafael