深奥

深奥	shēn ào	profound / abstruse / recondite / profoundly
深	shēn	old variant of 深
深	shēn	deep (lit. and fig.)
奥	Ào	(bound form) Austria (abbr. for 奥地利) / (bound form) Olympics (abbr. for 奥林匹克)
奥	ào	obscure / mysterious