How exactly do I “understand” the meaning behind a group of kanji?

I’m a fan of Code Geass, and while studying the lore for a fanfic, I came across a these 炎帝倒寿 -*Entei Touju*\- Kanjis with no translation -litteral or figurative-, so I’ve done some research. 炎帝倒寿 being the name of somekind of mystical tool/weapon, I assume that there’s somekind of meaning behind these specifics ideograms. While the first two Kanji were pretty simple – 炎帝 *Entei* can be translated as “Flame Emperor”-, the latter two -倒寿 *touju*\- are less obvious.

I understand that 倒 can mean “Overthrow” or “Fall” and 寿 can mean “longevity”, “age”, “life”. While I understand that Kanjis don’t have exact translations, there’s supposed to be an idea, a meaning, behind any kanji and kanji combination. Yet I can’t see this “meaning”.

Like 日本 *Nihon*, the first Kanji means “Day” or “Sun”, and the other “Book” or “Origin”. Together it makes “Sun Origin”, which fits for a country that his know in the west as “The land of the rising sun”.

Or 夜想宝具, also from the Code Geass lore, which is read as “Nightmare”, but writtent with the kanjis for Night, Thought/Perception, Treasure and Tool. Given Code Geass lore, I can see why using these ideograms.