כָּשֵׁר
kasher
English from Hebrew
“A word for 'fit and proper' in Jewish law became English slang for anything legitimate.”
Kosher (כָּשֵׁר, kasher) means 'fit, proper, correct' in Hebrew. In Jewish dietary law (kashrut), it describes food prepared according to specific biblical and rabbinical rules.
The dietary laws are complex: separation of meat and dairy, specific slaughter methods, prohibited animals. Kosher is not just about what you eat but how the entire food system is organized — from field to table.
Yiddish-speaking immigrants brought 'kosher' to America. By the mid-20th century, it had broken free of food: 'Is this kosher?' means 'Is this legitimate? Is this above-board?'
The secular meaning perfectly captures the original: kosher was never just about food safety. It was about living correctly, acting properly, meeting a standard. The metaphor was always there.
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Today
Kosher food is now a $24 billion industry worldwide, bought by many non-Jews who trust the certification as a quality standard.
The slang usage — 'Is this kosher?' — has become universal English. A 3,000-year-old dietary concept became a general word for legitimacy.
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