Meaning

noun a small stream

noun a small channel (as one formed by soil erosion)

originFrom or akin to West Frisian ril (“rill; a narrow channel”), Dutch ril (“rill; gully; trench; watercourse”), German Low German Rille, Rill (“a small channel; brook; furrow”), German Rille (“a groove; furrow”).

Etymology from Wiktionary, CC BY-SA 3.0