*ahtōutēhundą

From *ahtōu (‘eight’) + the analogical decade element **-tēhundą, ultimately continuing a decimal formation meaning something like ‘eight tens’ (Ringe 2017: 230). The Proto-Germanic form is secondary. Ringe’s (2017: 230–31) account, based on (Szemerényi 1960: 34–35), says that earlier **-ēhund- arose in pre-Germanic *fimfēhund- (‘fifty’), with the original *-ē- of *fimfē (‘five’) later reanalyzed as a linking vowel, which then spread to *sehsēhund- (‘sixty’) and then *sebunt-ēhund- (‘seventy’), which was later reanalyzed after the loss of final *-t in *sebun, as **sebun-tēhund-. This newly abstracted ‘decad’ suffix **-tēhund- then spread analogically to ‘eighty’ and ‘ninety’, yielding *ahtōu-tēhundą and *newun-tēhundą, respectively. Subsequently, the forms for ‘twenty’ through ‘sixty’ were replaced with periphrastic forms including *tigiwiz, plural of *teguz (a u-stem derivation possibly reflecting a zero-grade collective or abstract noun) < *tehun (Neri 2003: 180–83), leading to the common forms seen in the Proto-West Germanic reflexes today, such as English -ty, Dutch -tig, West Frisian -tich, and German -zig, as well as in many of the decad reflexes of Old Norse.