Abstract: On the Web and in traditional media, we are witnessing an explosion of neologisms of the form [éco-X]: écobéton, écoserre, etc. The analysis of these neologisms shows that the sequence éco- is semantically underspecified, that [éco-X] exerts almost no constraint on X, whatever its nature, and that éco- is a “family duplicator” that can be applied to all the members of a derivational family, provided that one of them expresses a ‘green’ concept.