The transiton -l>-w is not uncommon. Germanic
-old/-olt/-ald/-alt > -oud/-out is typical for Dutch (only before -d and -t).
It also appeared (at the same time? cf. bilinguism in the Franconian kingdom?)
in old French in a wider context, eg, her(w)ald>héraut,
cheval/chevaux, al>au, del>du, etc. Portugese also shows a weakeing
or loss" of -l. Portugese & French are the Romance langages with
the largest stress, and both languages show nasalisation. I wonder if these
phenomena might be related?
Marc