Grimm's law
Sometimes subsequent developments can treat the forms with and without the s-mobile quite differently. For example, by Grimm's law PIE becomes Proto-Germanic "f", but the combination is unaffected by this. Thus the root "", perhaps meaning 'scatter' has two apparently quite dissimilar derivatives in English: "sprinkle" (from nasalized form *"sprenk-") and "freckle" (from *"prek-").