Mid 19th century; earliest use found in James Dana (1813–1895), geologist, zoologist, and teacher. From German Meroxen from scientific Latin meroxenus (in Astrites meroxenus), probably from mero- + ancient Greek ξένος unknown, strange, probably so named from the fact that uniaxial mica, which had formerly been regarded as a single species, actually comprised a group of species, and hence the members of this group had previously been ‘partly unknown’.