We don't have synonyms for etherin yet — it may be a rare, specialized, newly coined, or misspelled word. The closest thesaurus entries we have are etheric, etheria and tetherin.
(n) :
(organic chemistry) A white crystalline hydrocarbon, regarded as a polymeric variety of ethylene, obtained in heavy oil of wine, the residue left after making ether.
(n) :
(organic chemistry) A white crystalline hydrocarbon, regarded as a polymeric variety of ethylene, obtained in heavy oil of wine, the residue left after making ether.