Where does “underdeck” come from?

underdeck (English) comes from English deck, from Middle English dekke, from Middle Dutch dec, from Middle Dutch decken, from Old Dutch thecken, from Proto-West Germanic þakkjan, from Proto-Germanic þakjaną, from Proto-Germanic þaką — to cover; pole, stick, beam.

underdeck (English): The part of a bridge that lies beneath the deck,...

Definitions

  1. The part of a bridge that lies beneath the deck,...

Ancestry of “underdeck”, step by step

underdeck traces back through two separate lines of ancestry.

via English deck

StepLanguageWordMeaning
1EnglishdeckAny raised flat surface that can be walked on: a...
2Middle Englishdekke
3Middle Dutchdecroof, covering
4Middle Dutchdeckento roof, to build/repair a roof; to cover; to...
5Old Dutchtheckento cover; to roof
6Proto-West Germanicþakkjanto cover; to burn
7Proto-Germanicþakjanąto cover; to burn
8Proto-Germanicþakąroof, cover
9Proto-Indo-European(s)teg-to cover; pole, stick, beam

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
Every word from Proto-Indo-European (s)teg-