Where does “greycoat” come from?

greycoat (English) comes from English Grey, from Middle English grey, from Old English grǣġ, from Proto-West Germanic *grāu, from Proto-Germanic grēwaz, from Proto-Indo-European ǵʰreh₁- — to become green, grow; to grow; to green, to grow.

Ancestry of “greycoat”, step by step

greycoat traces back through two separate lines of ancestry.

via English Grey

StepLanguageWordMeaning
1EnglishGreyA member of the Royal Scots Greys, a cavalry...
2Middle Englishgreygrey, dull, drab; glinting, glistening; grey
3Old Englishgrǣġ
4Proto-West Germanic*grāugrey
5Proto-Germanicgrēwazgrey
6Proto-Indo-Europeanǵʰreh₁-to become green, grow; to grow; to green, to grow

via English coat

StepLanguageWordMeaning
1EnglishcoatAn outer garment covering the upper torso and...
2Middle EnglishcoteA coat, especially one worn as an undergarment or...
3Old Frenchcotteovershirt, tunic
4Frankishkottacoat
Every word from Proto-Indo-European ǵʰreh₁-