cient ▁Greek ▁ θ υ ρ ο ε ι δ ή ς ▁on ▁the ▁other ▁side , ▁as ▁the ▁latter ▁does ▁not ▁mean ▁shield - like , ▁but ▁actually ▁means ▁like ▁a ▁door , ▁derived ▁from ▁ θ ύ ρ α , ▁door . ▁ Θ υ ρ ο ε ι δ ή ς ▁is ▁however ▁used ▁in ▁an atomic ▁nom en cl ature ▁in ▁the ▁expression ▁ θ υ ρ ο ε ι δ έ ς ▁ τ ρ ῆ μ α ▁( τ ρ ῆ μ α ▁= ▁hole , ▁per for ation , ▁a pert ure ), ▁co ined ▁by ▁the ▁Greek ▁phys ician ▁Gal en . ▁An cient ▁Greek ▁ θ ύ ρ α ▁can ▁be ▁translated , ▁besides ▁the ▁a for ement ioned ▁door , ▁as ▁gate , ▁entrance ▁and ▁opening . ▁The ▁Greek ▁name ▁ θ υ ρ ο ε ι δ έ ς ▁ τ ρ ῆ μ α ▁for ▁this ▁opening ▁between ▁the ▁os ▁pub is ▁and ▁the ▁os ▁is ch ii , ▁currently ▁called ▁obt ur ator ▁for amen , ▁clearly ▁origin ates ▁from ▁its ▁being ▁an ▁opening ▁( θ ύ ρ α ), ▁while ▁bearing ▁no ▁res embl ance ▁to ▁a ▁shield ▁( θ υ ρ ε ό ς ). ▁The ▁Latin ▁translation ▁for amen ▁thy re o ide um ▁for ▁ θ υ ρ ο ε ι δ έ ς ▁ τ ρ ῆ μ α ▁by ▁the ▁ 1 8 th – 1 9 th - century ▁German ▁phys ician ▁and