The story
By surface analysis, dead + nettle; cognate to German Totnessel. Compare Dutch dovenetel, German Taubnessel, North Frisian Duufnäädel (all of which are literally "deaf-nettle").
Etymology from Wiktionary, CC BY-SA 4.0.
deadnettle
Today it means: Any plant of a species in genus Lamium, which closely resembles the nettle, but does not possess stinging hairs. Full definition →