In Modern West Frisian, by New Frisian Breaking, two
rising diphthongs have developed with initial /w/. However, in the
eastern part of the language area these sequences are nowadays
pronounced as [jo] and [ja], respectively. The change started when
immigrant peat diggers became integrated into Frisian society, and
as a result of imperfect learning did not master fully those difficult
Frisian diphthongs. As an escape strategy, they fronted the initial
glide to /j/. A second centre of hange was at the language border,
where peat-digging also resulted in the mixing of populations. In
the course of the 20th century, the new forms were rapidly spreading.
An analysis of the change as a case of shift (cf. Thomason and
Kaufman 1988) can nicely explain the platalization of the glide,
and moreover, it gives insight into the question why this only occurred
after labials. In the case of a minority-majority contact situation,
however, change by shift in the minority language is not to
be expected in the first place, as it requires that a population is
switching to a target language that is less powerful or prestigeous.
However, the peat diggers all spoke a Dutch Low Saxon dialect,
which had a low prestige, indeed.