Where does “deep blue sea” come from?

deep blue sea (English) comes from English deep, from Middle English dep, from English department, from French département, from Middle French département, from Old French département, from Old French departir, from Latin departiō — afterwards, post; by, at.

deep blue sea (English): The sea, the ocean, the open sea

Definitions

  1. The sea, the ocean, the open sea

Ancestry of “deep blue sea”, step by step

deep blue sea traces back through 3 separate lines of ancestry.

via English deep

StepLanguageWordMeaning
1Englishdeep"Extending far away from a point of reference,...
2Middle EnglishdepAlternative form of depe
3EnglishdepartmentA part, portion, or subdivision; A distinct...
4Frenchdépartementdepartment; département
5Middle Frenchdépartement
6Old Frenchdépartement
7Old Frenchdepartirto leave; to depart; departure
8Latindepartiōto divide
9Latindē-of; from
10Latinof; concerning; about
11Latinpostbehind; after, since, besides, except; behind,...
12Latinposteablative singular of postis
13Proto-Italicpostibehind, after
14Proto-Indo-Europeanpóstiafter
15Proto-Indo-Europeanpósafterwards, post; by, at

via English Blue

StepLanguageWordMeaning
1EnglishBlueA letterman at Oxford or Cambridge; A member of...
2Middle Englishblēwe
3Anglo-Normanblewblue
4Middle Frenchbleublue
5Old Frenchblöeblue
6Latvianblāvusaccusative plural masculine form of blāvs
7Old High Germanblāoblue, dark, grey; blue; yellow
8Proto-West Germanicblāublue
9Proto-Germanicblēwazblue; a dark bluish or grey colour, black
10Proto-Indo-Europeanbʰlēw-yellow, blond, grey

via English sea

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;...
Every word from Proto-Indo-European pósEvery word from Latin dē-Every word from Proto-Indo-European pósti