Is it not odd that there were two Enochs (Gen 4:17 and 5:18) in early times?

This is only the first of many instances of names with many bearers in the Bible. There are two Lamechs in the two different lines as well. There seems little reason to find significance in this particular juxtaposition. There are two or four Enochs in the Bible, depending on whether one counts “Hanoch” as the same name (the Septuagint renders them the same). The name means something like “initiated, inaugurated, trained.” Both men called “Enoch” might well have been initiated in the ways of their fathers.