Luis (ᚂ) is the second letter (Irish "letter": sing.fid, pl.feda) of the Ogham alphabet, derived either from luise "flame" or from lus "herb". Its Proto-Indo-European root was either *leuk- 'to shine' or *leudh- 'to grow'. Its phonetic value is [l]. If the letter name follows the same pattern as ruise to ruis, it is likely that the letter was originally named from luise, though different kennings point to both meanings.