What's the difference between i.e. and e.g.?
"small brook, rivulet," 1530s, from or related to Dutch and Frisian ril, Low German rille "groove, furrow, running stream," probably from Proto-Germanic *ril- (cf. Old English rið, riþe "brook, stream," which survives only in dialects), a diminutive form from PIE root *reie- "to run, flow" (see Rhine).
any of various valleys or trenches on the surface of the Moon. The term was introduced by early telescopic observers-probably the German astronomer Johann Schroter about 1800-to denote such lunar features. The word rima (from Latin, "fissure") is often used for the same kind of features.