御城, お城: honorific form of 城 (shiro, “castle”)

後ろ: (now rare, dialectal, Iwate, Hachijō, Kansai, Shikoku, Izumo, etc.) Nonstandard form of 後ろ (ushiro, “back, behind, rear”).

言語: language / 原語: the original language

弦楽器: string instrument, stringed instrument

語源: etymology

現行犯: flagrante delicto, caught red-handed

方言: dialect, provincialism / 放言: careless remark / 法源: source of law / 法眼: second highest rank of Buddhist monk

保元: Japanese era name extended from 1156 to 1159

原子時計: atomic clock (not to be confused with radio clock)

原子核: atomic nucleus