Reconstruction:Proto-Germanic/-ô

Etymology 1
. Possibly a fossilised form of the Proto-Indo-European thematic ablative *-eh₂d, in which case it would reflect earlier *-ôt before word-final -t was lost.

Adverb

 * 1)  -ly.

Descendants
This suffix lost its function in some Middle 🇨🇬 languages, where adverbs eventually became identical to the base adjectives they were formed from.

Etymology 2
From. Proto-Germanic masculine n-stems continue Proto-Indo-European amphikinetic n-stems, meaning the vowel grade in the root, the suffix, and the ending alternated throughout the paradigm. Stem ablaut was not preserved in any later Germanic language, but it is indirectly tangible through such pairs as English and German. Suffix ablaut is clearly visible in the paradigm below, by way of the *ô ~ *a ~ *i alternation.

Noun

 * 1)  -er.