history effect: in an experiment, the effect that external factors, unrelated to the experiment, have on the subjects during the time of the experiment. When you assess your results, the difference between your pro test (before) and your post test (after) has been affected by the external event.

maturation effect: internal changes within the subjects that occur over the course of time.

For a description of the French terms, see: http://www.unige.ch/ses/socio/stassen/ACES211.ppt

There are a number of interesting definitions and examples to be found if you google for “history effect” “maturation effect” [http://tinyurl.com/c6xau], such as this one:
http://www.naropa.edu/faculty/johndavis/prm2/exper3.html