Matzah balls (קניידלעך pl., singular קניידל ; with numerous other transliterations) or matzo balls are Ashkenazi Jewish soup morsels made from a mixture of matzah meal, beaten eggs, water, and a fat, such as oil, margarine, or chicken fat. Matzah balls are traditionally served in chicken soup and are a staple food on the Jewish holiday of Passover, though they are not eaten during Passover by those who observe a prohibition on soaking matzah products. The texture of matzah balls may be light or dense, depending on the recipe. Matzah balls made from some recipes float in soup; others sink. Although there are official transliterations of Yiddish words into English by the YIVO Institute, there are many non-standard transliterations. Alternate transliterations of the Yiddish term for matzah ball, in the singular, include: knaidl, knaidel, kneidl, and kneidel. Transliterations in the plural include: knaidels, knaidlach, knaidelach, kneidels, kneidlach, kneidelach, kneydls, kneydels, and kneydlach. The various transliterations of the term gave rise to minor controversy in June 2013, when it was the winning word in the Scripps National Spelling Bee. Thirteen-year-old Arvind Mahankali of New York spelled "knaidel" correctly in accordance with Webster's Third New International Dictionary, the official dictionary of the Bee, to become the champion. However, there was controversy whether that was indeed the definitive spelling of the term, with others preferring "knaydel", "kneydel", "knadel", or "kneidel". See Knödel for further information about the origin of the word and the food itself. The exact origins of matzo balls – and the traditional matzo ball soup – are unknown. Some historians posit that the copious amounts of matzo meal produced during the Industrial Revolution in the 19th century[Incomplete thought—needs elaboration], others believe that Jews used the crumbs leftover from matzo baking to produce the filling additions to their soup.