Folk

PGmc. *fulka- is often listed among suspected substratal loans. Most
dictionaries derive it from PIE *pleh1-, but the traditionally suggested
protoform *pl.h1-g(^)o-m involves an unexplained suffix. I'd like to
propose a simpler derivation: we may be dealing with a thematised form
of *PIE *pl.h1u- 'many, much', i.e. *pl.h1w-o-m > pre-Gmc. *pulgaN >
*fulka-. This variety of "Verschärfung", affecting intersonorant
"laryngeal + *w" combinations (presumably via something like *-hW- >
*-G-), is visible e.g. in *nah2w- + -o:n > *nago:n > *nakan- 'ship' and
*gWih3wo- > *gWigWa- > *kWikWa- 'alive' (*h3 preserves labialisation).
It's older than Seebold's pre-Germanic change of *w > *g between a
sonant and *u, and of course older than similar changes in individual
Germanic languages (cf. *niwun- ~ *nigun- 'nine').

Piotr