The sources of some of the vowel runes of the futhark, the oldest Germanic writing system, are not clear. The a rune has the place and shape of Phoenician H (He), Greek Ε, Latin E, and owes its sound value in the futhark to the North and West Germanic sound change +ē > +ā (Vennemann 2009: 843-845). The u rune has the place and shape of Phoenician G (Gimel), Greek Γ, Latin C, and owes its sound value to the late Punic weakening of g to J (Vennemann 2013: section 2). The i and o runes appear to be unproblematic, though they may not be; e.g., it is unclear why o stands near or at the end of the rune row and is marked by diacritic tails. But the yew rune ï and the e rune are truly enigmatic and have been much discussed. The present article offers explanations for all four still difficult vowel runes, ï, i, e, and o: It is shown that all four derive from Neo-Punic consonant letters, ï and i from Y (Yodh), e from H (He), and o from ¨ (‘Ayin), as these were regularly employed for indicating the vowels [i], [e], and [a], respectively, especially in Latin loanwords and names.