The phrase "wo, wo" is a Hebraism meaning "great wo," "much wo," or "exceeding wo." Repetition was commonly used in Biblical Hebrew for emphasis or to intensify an attribute. See Ecclesiastes 7:24 where "exceeding deep" reads "deep, deep" in the Hebrew text. [Zarahemla Research Foundation, Study Book of Mormon, p. 4]
Nephi comments that in Lehi's vision, Lehi was given a book in which he read concerning the destruction of Jerusalem: "Wo, wo, unto Jerusalem, for I have seen thine abominations." Nephi also comments that "many things did my father read concerning Jerusalem--that it should be destroyed, and the inhabitants thereof" (1 Nephi 1:13).
According to Amy Hardison, along with covenant blessings, ancient Near Eastern treaties and covenants contained covenant curses. Curses were basically a reversal of blessings, though the curses were typically far more detailed and extensive. Covenants were written with a specific vocabulary. Inside the covenant context, certain words had official and legal meanings that sometimes differed from their normal, everyday use. For instance, "woe" is the pronouncement of a covenant curse, and to do "evil" is to break one's covenant. Evil in covenant curses conveys disaster, calamity, and misfortune--not the moral opposite of righteousness. [Amy Blake Hardison, "Being a Covenant People," in Covenants Prophecies and Hymns of the Old Testament, pp. 24, 28]