Ben McGarr said or asked:
>(1) Germanic ... under strong Celtic influence
This has been tried in the literature, but there is no clear agreement, and
good reasons to reject the idea in its simplest form. Several attempts
havebeen made to argue for Germanic as a language of one kind heavily
influenced by another, but few people have ended up convinced.
There is now a recognition that these theories all presuppose there is
something "wrong" or "un-IE" like about Germanic. This view is now widely
challenged, especially since:
(a) the glottalic theory suggested that Germanic may preserve rather than
shift the sounds of PIE, and
(b) the widening agreement (though perhaps still without general
consensus, as far as I know), that Greek and Indo-Iranian are somewhat
innovative, especially in the verbal system.
Germanic does have particular peculiarities, but then so does every group -
or it would not be a separate group!
>... Celtic names of some of the leaders of the Cimbri and Teutones as
transliterated in Classical accounts.
The Cimbri and Teutones were indeed Germanic tribes, but on their way from
roughly Belgrade (they started in Jutland) north of the Alps into Gaul, they
were joined by the Tigurini and other Celtic tribes. This may explain why
Celtic names pop up in descriptions of these tribes. The Celts got all
over the place, and if my memory is right, even into Greece about 300 AD.
> [How] the Germanic languages ... tie in with other IE families, structure
and original vocabulary?
Germanic lies between Celtic and Baltic, and shares features of structure
and phonology with both those groups. It shares vocabulary with a
"North-Western" group, which may simply be a default group, including
particularly Celtic and Baltic, but to some extent also Italic and Slavic.
Germanic does have a proportion of vocabulary which appears to be non-IE,
the origin of which is still unsure. The features of syntax which seem
unique to it (e.g. the weak endings on nouns and adjectives) can be traced
back to PIE elements. It is assumed that even the -d element on weak verbs
is from PIE, although the precise origin is disputed.
Proto-Germanic, reconstructed from the various attested Germanic languages,
shows a strikingly close affinity to PIE, despite phonetic changes.
Hope that answers your questions!
Peter