Where does “ridingcoat” come from?

ridingcoat (English) comes from English riding, from English trithing, from Middle English trithing, from Old English þriðing, from Old Norse þriðjungr, from Proto-Germanic þridjô, from Proto-Indo-European tretyós, from Proto-Indo-European tr̥tyós — three.

Ancestry of “ridingcoat”, step by step

ridingcoat traces back through two separate lines of ancestry.

via English riding

StepLanguageWordMeaning
1Englishridingpresent participle of ride; A path cut through...
2EnglishtrithingOne of three ancient divisions of a county in...
3Middle Englishtrithing
4Old Englishþriðing
5Old Norseþriðjungrthird part
6Proto-Germanicþridjôthird
7Proto-Indo-Europeantretyós
8Proto-Indo-Europeantr̥tyósthird
9Proto-Indo-Europeantréyesthree

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 tréyes