Where does “thritti” come from?

thritti (Middle English) comes from Old English þritiġ, from Proto-Germanic þrīz tigiwiz — thirty.

Ancestry of “thritti”, step by step

StepLanguageWordMeaning
1Old Englishþritiġthirty
2Proto-Germanicþrīz tigiwizthirty
Every word from Proto-Germanic þrīz tigiwiz →Every word from Old English þritiġ →