Author of genus is Hagen, 1861. From eryth- (?), Greek, meaning red, plus the ubiquitous suffix -themis. This is from Greek, first used by Hagen in 1861, and it means "what has been established", i.e., rule, or law. Themis was also a goddess of order and justice. However, it is possible the suffix was also simply based on the Greek suffixes -hemis (half), or -emis. See this Odonata list post by KD Dijkstra.
