Many of the western books came to Japan through the Netherlands (阿蘭陀, Oranda) and were called the books of the Netherlands, '蘭書 (Ransho),' and those western studies from the other parts of Europe were also called the learning of the Netherlands, '蘭学 (Rangaku).'
洋書の多くは都合オランダ経由で入ってきたためオランダ（阿蘭陀）の書物「蘭書」と呼びオランダ以外の西洋学問のこともオランダ（阿蘭陀）学問「蘭学」で呼ぶようになった。