Thread:User talk:CodeCat/PGmc prepositions and adverbs/reply (7)

The ablative probably merged into the instrumental in Germanic. It's hard to be sure, because there are so few clear uses of instrumentals attested. Most of the attested languages use the dative in ablative function, but they also generally merge the instrumental with the dative, so that doesn't tell us much. It's quite possible that the ablative merged straight into the dative.

The ending -ē would probably be an old consonant stem instrumental, but consonant stems themselves were becoming rare, so it's a bit unusual that such an ending would become widespread. You'd expect the a-stem ending -ō to take over that role instead. The ablative ending would have been -ô for a-stems, which is probably where the adverb ending came from. I don't think consonant stems had a separate ablative ending in PIE, but maybe there was an innovation and it's the source of the -ê that's found in Gothic.