Where does “rain man” come from?

rain man (English) comes from English MAN, from English manual, from Middle English manuel, from Anglo-Norman manuel, from Old French manual, from Latin manuālis, from Latin manus, from Proto-Italic manus — human being; man; hand.

rain man (English): An autistic, or mentally and/or socially impaired...

Definitions

  1. An autistic, or mentally and/or socially impaired...

Ancestry of “rain man”, step by step

rain man traces back through two separate lines of ancestry.

via English MAN

StepLanguageWordMeaning
1EnglishMANInitialism of Metropolitan Area Network
2EnglishmanualA handbook; A booklet that instructs on the usage...
3Middle Englishmanuel
4Anglo-Normanmanuelmanual; done with the hands; handle; manual;...
5Old Frenchmanual
6Latinmanuālishand
7Latinmanushand; bravery, valor; violence, fighting
8Proto-Italicmanushand
9Proto-Indo-Europeanman-human being; man; hand

via English rain

StepLanguageWordMeaning
1EnglishrainCondensed water falling from a cloud; Any matter...
2Middle Englishreynrain water falling from a cloud
3Old Englishreġnrain
4Proto-West Germanicregnrain
5Proto-Germanicregnąrain
6Proto-Indo-EuropeanHreǵ-to flow
Every word from Proto-Indo-European man-Every word from Proto-Italic manusEvery word from Latin manus