Instead, he argues, this development has been artificially frozen in an "intermediate" state by the standardisation of Dutch pronunciation in the 16th century, where lowered diphthongs found in rural dialects were perceived as ugly by the educated classes and accordingly declared substandard. Now, however, in his opinion, the newly affluent and independent women can afford to let that natural development take place in their speech. Stroop compares the role of Polder Dutch with the urban variety of British English pronunciation called Estuary English.

What word did Stroop use to describe the static stage of diphthong pronunciation?