In looking at the pictures from The Wind Waker and the Book of Kells, one of my readers noticed that the script used for the Hylian text looked familiar. Here’s a chart from Nintendo for translating:
Futhark were used in Germanic languages before the Latin alphabet. They were primarily used for inscriptions in wood and stone, not for usages on paper such as letter-writing, though some runic writing on paper does exist. Ogham was used for similar purposes in the Old Irish and Brythonic languages. Both futhark and ogham vary throughout the centuries depending on time period and dialect of usage.
The Book of Kells was written in Latin, so I can’t use these examples to draw parallels between The Wind Waker and the Book of Kells, but some parallels still remain between The Wind Waker and Celtic culture. The Hylian script, futhark, and ogham share similarities in that they use many horizontal strokes for a blocky end result. The Hylian script, futhark, and ogham all appear to have been written with a pen (or digital line tools). In comparison, the Hylian script from older Zelda games bears greater resemblance to Japanese and is clearly intended for brush writing. Considering the way that The Wind Waker departs from a brush-style script, the number of horizontal lines that resemble ogham, and the other Celtic influences on the game, it seems even more likely that The Wind Waker was at least in part inspired by Celtic culture.