ledhu

This word is highly debated. I wouldn't claim that "lith" cannot mean both "ash" and "sand", as natural languages permit stranger polysemies than that. But I do think there's a reasonable linguistic case that this merger is unusually unsupported cross-linguistically and that distinguishing the two concepts would improve the lexicon with very little cost. I have used √LIT "grit" + ✶-mā "instrumental suffix", in analogy to √SAG "bitter, poison" + -mā = ✶sagmā "poison".