Passover
2 of the 7 encyclopedias on this shelf carry an entry for Passover. Both are reproduced below, so you can see where they agree and where they differ.
Collier's New Encyclopedia (1921)
a festival instituted to commemorate Jehovah's "passing over" the Israelite houses while "passing sing through" those of the Egyptians, to destroy in the latter all the first-born (Exod. xii: 11, 12, 23, 27). The first passover (that in Egypt), those subsequently occurring in Old Testament times, and those of the New Testament and later Judaism, were all somewhat different. In the first of these a lamb without blemish was taken on the 10th, and killed on the 14th, of the month Abib, thenceforward in consequence to be reckoned the first month of the ecclesiastical year. The blood of the lamb was to be sprinkled on the two side posts and the single upper door post, and the flesh eaten "with unleavened bread and bitter herbs" before the morning (Exodus xii: 1-13). That night Jehovah, passing over the bloodstained doors, slew the first born in the Egyptian houses not similarly protected; and, as the emancipated Jews that night departed from Egypt, that first passover could have continued only one day. But the festival was to be an annual one. Connected with it was to be a feast of unleavened bread (Exod. xii: 14-20; Num. xxviii: 16). Sometimes the term passover is limited to the festival of the 14th of Abib; sometimes it includes that and the feast of unleavened bread also, the two being viewed as parts of one whole (Ezek. xlv: 21). When the Jews reached Canaan, every male was required to present himself before God thrice a year, viz., at the passover, or feast of unleavened bread, at that of "harvest," and that of "ingathering" (Exod. xxiii: 16). In the Old Testament six passovers are mentioned as having been actually kept. In modern Judaism no lamb is sacrificed, but the shank bone of a shoulder of that animal is eaten, leaven put away, and other ceremonies observed.
Aiton's Encyclopedia (1910)
an annual feast of the Jews. It falls on the first full moon of the spring, about Easter time. It is a feast of thankfulness, corresponding in a way to the American Thanksgiving. It was instituted to commemorate the escape of the Hebrews in Egypt, when the Lord, smiting the first born of the Egyptians, "passed over" the homes of the Israelites, the doorways of which were marked with the blood of the pascal lamb. The Israelites were directed to eat the first Passover with their loins girded, shoes on their feet, and staffs in their hands. "And ye shall observe this thing for an ordinance to thee and thy sons together. And it shall come to pass when your children shall say unto you, what mean we by this service? that ye shall say, It is the sacrifice of the Lord's passover, who passed over the houses of the children of Israel in Egypt, when he smote the Egyptians." The term came to include the entire week in which unleavened bread is eaten. In this sense, it is synonymous with the feast of unleavened bread. When settled in Canaan, the feast of the Passover was celebrated at Jerusalem. All who were able to leave home came up to the temple. Josephus tells us that, in the year 65 A. D., 3,000,000 Jews visited Jerusalem to eat the feast of the Passover. A quarter of a million lambs were required. The city could not hold the multitude. Tents were erected without the walls. This festival was the great event of the year. It reminds the reader of the annual pilgrimage to Mecca still enjoyed by the Arabs, a kindred people. The festival of the Passover is now celebrated widely in the home, like the American Thanksgiving.