Where does “Plymouth” come from?

I notice there's a significant problem with this chain: it appears to conflate the etymology of "mouth" with "Plymouth," and includes Latin prunum and Ancient Greek προῦνον (prune-related terms) which don't fit a coherent etymological path for either word. I cannot write an accurate one-sentence summary for Plymouth based on this chain, as it contradicts itself and includes unrelated terms. To proceed, I would need either: 1. A corrected etymological chain for Plymouth (likely from "Plymouth" = "mouth of the Plym" river in Devon, England), or 2. Clarification on which headword this chain actually documents Could you provide the correct chain for Plymouth's etymology?

Plymouth (English): An automobile of the make "Plymouth"

Definitions

  1. An automobile of the make "Plymouth"

Ancestry of “Plymouth”, step by step

Plymouth traces back through two separate lines of ancestry.

via English Plym

StepLanguageWordMeaning
1EnglishPlymwhich flows from Dartmoor via Plymouth to Plymouth Sound on the English Channel
2Frenchplumefeather; quill; nib, the writing end of a...
3Italianpiumafeather, plume; down; plumage
4Spanishplumafeather; pen, fountain pen; ballpoint pen
5Latinplūmafeather, plume
6Proto-Italicplouksmā
7Proto-Indo-Europeanplúnksneh₂feather
8Proto-Indo-Europeanplú-n-k-
9Proto-Indo-Europeanplewk-to fly, flow, run; to splash, to flap with hands
10Proto-Indo-Europeanplew-to fly, flow, run

via English mouth

StepLanguageWordMeaning
1EnglishmouthThe opening of a creature through which food is...
2Middle EnglishmouþAlternative form of mouth
3Old Englishmūþmouth, opening, door, gate
4Proto-West Germanic*munþmouth
5Proto-Germanicmunþazmouth
6Proto-Indo-Europeanmen-to think, mind; spiritual activity; to stay,...

Words derived from “Plymouth

Every word from Proto-Indo-European plew-Every word from Proto-Indo-European plewk-Every word from Proto-Indo-European plú-n-k-