late 14c., "to shine brightly;" early 15c., "to shine dimly," perhaps from or related to Middle Dutch glimmen, Middle Low German glimmern, from an extended (frequentative?) form of Proto-Germanic *glim-, which also is the base of Old English glæm "brightness" (see gleam (n.)). Sense shifted 15c. to "shine faintly." Compare Dutch glimmeren, German glimmeren "to shine dimly." Related: Glimmered; glimmering.