Where does “seagull” come from?

I need to flag an issue: the etymology chain provided doesn't support "seagull" as a headword. The chain traces "sea" (sǣ, see, wai, se, sed-, sed-, -os), but "seagull" is a compound of "sea" + "gull," and no etymology for "gull" is provided. I cannot write an accurate one-sentence origin summary for "seagull" using only this chain, as it would require inventing the missing etymology of "gull." Could you provide: 1. The complete chain for "seagull" itself, or 2. Clarification that the headword should be "sea" instead?

seagull (English): Any of several white, often dark backed birds of...

Definitions

  1. Any of several white, often dark backed birds of...

Ancestry of “seagull”, step by step

StepLanguageWordMeaning
1EnglishseaA large body of salt water; A lake, especially if...
2Middle Englishseesea, ocean; A body of water, a lake; seat, chair
3Old Englishsea, lake
4Proto-West Germanicsaiwisea
5Proto-Germanicsaiwizsea, ocean
6Proto-Germanicsīhwanąto filter
7Proto-Indo-Europeanseykʷ-to moisten; to filter
8Proto-Indo-Europeansey-to be wet; dribble; run; to stretch one's arm;...

Words derived from “seagull

Every word from Proto-Indo-European sey-Every word from Proto-Indo-European seykʷ-Every word from Proto-Germanic sīhwaną