Though Jews have famously written many of today’s popular Christmas songs, there’s an additional layer of characteristically Jewish irony in hearing those tunes sung in Yiddish — the widespread language of Eastern European Jews before the Holocaust is likely the last one associated with the late-December Christian holiday.

But is the account of Yiddish Christmas carols factual or a historical bubbe meise?

In his new book, “Christmas in Yiddish Tradition: The Untold Story,” Jordan Chad explores the folklore of  Yiddish-speaking Jews in Central and Eastern Europe from the Middle Ages through the Modern period. The study reveals that Christmas was surprisingly one of European Jews’ favorite days of the year, and how Christmas traditions were once transmitted in Yiddish — a language non-Jews didn’t often speak.

Chad, 31, is a researcher in physics, mathematics, neuroscience, and Yiddish at the University of Toronto.

“At one point, as a side project, I translated an old Yiddish booklet on the theory of relativity that was written in Yiddish under Einstein’s supervision by one of his students… Then I started thinking, ‘I wonder what else there is in Yiddish that people don’t know about, what is there besides the Sholom Aleichem stories and the romanticized shtetl stories?'” Chad said in a recent interview with The Times of Israel.

“I was digging deeper into Yiddish memoirs and folklore… I started going beyond physics and Yiddish and got into Christmas in Yiddish. And that’s how this book came along,” he said.

Chad delved into Yiddish memoirs and other accounts of Jewish life in Western Europe, and later in regions such as Russia, Poland, Belarus, and Ukraine.

“Very consistently in the Yiddish literature, memoirists would write about their favorite yontif [holiday] when they were a child. They called........

© The Times of Israel