Where does “buy into” come from?

buy into (English) comes from English into, from Middle English in-to, from Old English intō, from Old English in, from Proto-West Germanic *in, from Proto-Germanic in, from Proto-Indo-European én — in.

buy into (English): To believe; to accept a craze or fad as valid; To...

Definitions

  1. To believe; to accept a craze or fad as valid; To...

Ancestry of “buy into”, step by step

buy into traces back through two separate lines of ancestry.

via English into

StepLanguageWordMeaning
1EnglishintoTo or towards the inside of; To or towards the...
2Middle Englishin-tointo
3Old Englishintōinto
4Old Englishinin; Alternative form of inn
5Proto-West Germanic*in
6Proto-Germanicinin; into
7Proto-Indo-Europeanénin

via English buy

StepLanguageWordMeaning
1EnglishbuyTo obtain in exchange for money or goods; To...
2Middle Englishbyento buy
3Old Englishbycġanto buy, pay for, acquire, redeem, ransom,...
4Proto-West Germanicbuggjanto buy
5Proto-Germanicbugjanąto deal; do business; exchange; to purchase; buy;...
6Proto-Indo-Europeanbʰewgʰ-to bend; curve, arch
Every word from Proto-Indo-European énEvery word from Proto-Germanic inEvery word from Proto-West Germanic *in