NUMBERS m . pl. is one of the books of the Torah or Tanakh. The 5 books of Moses, which constitute the Old Testament are Genesis, Exodus, Leviticus, Numbers, and Deuteronomy. The Greeks called it Pentateuch and Numbers comes from the Greek "Arithmoi" (which also gives rise to arithmetic, handling of numbers) In Hebrew the fourth book is called BAMIDBAR, 'in the desert', because it narrates the departure from Egypt and the wandering of the Jewish people for 40 years through the desert to reach the promised land, so that only free people who had never been slaves would arrive. Someone in their 40s 5000s was an elderly survivor. 2 . Obviously numbers is the plural of number, cipher, but I doubt anyone would be interested in consulting this meaning in a dictionary, when the word is understood and known before learning to read, around 2 to 3 years old.