When the Torah relates in this week’s parsha that Moshe Rabbeinu counted the Jews in the wilderness, it lists the head families of each tribe, who were ultimately the forbearers of the whole of Klal Yisroel. To each family name, the letter ה was added at the beginning of the name and the letter י was added at the end. Thus, the descendants of Reuven’s oldest son, חנוך , are referred to as משפחת החנוכי , and the descendants of his second son, פלוא , are referred to as משפחת הפלואי , and so on for all the other families in Klal Yisroel.