While various corded ware linked groups in eastern Europe have been linked to ancestors of the Slavs, Balts and Indo-Iranians, noone seems to have a clear idea as to what the big chunk of corded ware east of Poland and as far west as the Rhine and Switzerland spoke.
I think there is an interesting situation in that zone in that beaker quickly overlapped a chunk of the corded ware in those areas. It is interesting too that pre-Germanic and pre-proto Celtic share identical vocab to do with religion, war etc which is peculiar to those two groupings and long pre-dates later borrowings between Celtic and Germanic. It has also been suggested that some of this peculiar shared vocab is also known in Finnish. That strikes me as suggestive that the Corded Ware/battle axe horizon could be the origin of the peculiar subset of shared - not borrowed - vocab between pre-proto-Celtic and pre-proto-Germanic. This shared vocab could have been absorbed c. 2500BC when beaker and corded ware overlapped from the Rhine to the Baltic. The Finnish link seem to me to point to corded ware rather than beaker being the origin of this shared vocab subset. Other than this shared subset they were very distinct branches.