Where does “underflavour” come from?

underflavour (English) comes from English under, from Middle English under, from Old English under, from Proto-Germanic under, from Proto-Indo-European h₁entér, from Proto-Indo-European h₁en — in; in, inside.

Ancestry of “underflavour”, step by step

underflavour traces back through two separate lines of ancestry.

via English under

StepLanguageWordMeaning
1EnglishunderIn or at a lower level than; As a subject of;...
2Middle Englishunderunder
3Old Englishunderunder, beneath
4Proto-Germanicunderamong, between; under, beneath; under
5Proto-Indo-Europeanh₁entérbetween
6Proto-Indo-Europeanh₁enin; in, inside

via English flavour

StepLanguageWordMeaning
1EnglishflavourBritain standard spelling of flavor
Every word from Proto-Indo-European h₁enEvery word from Proto-Indo-European h₁entérEvery word from Proto-Germanic under