*-ē

Uncertain. Sometimes cited as *-ê (overlong/trimoric e). Fulk (2018: 238–39) describes the common adverbial suffixes as Proto-Germanic *-ē in alternation with *-ō, reflecting an o-stem ablative singular inflection, Proto-Indo-European *-ēd ~ *-ōd, giving PGmc *-ēt ~ *-ōt with eventual loss of the final dental. He notes, however, that the evidence for *-ēd is poor. Kieckers (1960: 94) derives this variant from PIE instrumental -ē (-*eh₁). Weiss (2009: 361), commenting on adverbial forming Latin ē, also suggests that it is possible that the -d is secondary and that these forms reflect the PIE instrumental *-eh₁, connecting the Latin suffix directly with PGmc. Fulk (2018: 238) notes that, in the descendants, Anglo-Frisian favored the *-ē variant, while the other daughter languages favored *-ō for adverbial formation. In addition to Latin, compare Proto-Slavic *-ě₂, a deadjectival adverb-forming suffix continued by Old Church Slavonic -ě, historically from a fossilized locative singular ending (Kahl 2024: 136–41). The Slavic formation is not necessarily directly cognate with the PGmc ending (though Kahl notes the possibility that an original adverbial formation from instrumental *-ě₁ < PIE *-eh₁ may have been simply replaced by or merged with the *-ě₂ formation). In any case, it provides a close Indo-European parallel for the development of adverbial suffixes from petrified nominal case forms.