Something different today! The term 五臓六腑 [ごぞうろっぷ] comes from traditional Chinese medicine. Its literal meaning is the five viscera and the six internal organs—organs as a TCM concept; not analogous to the anatomical organs. But 五臓六腑 can also mean guts/innards more generally, or figuratively, what's inside your heart. (Though in this case, it's just the name of a nice sushi place.)
Breaking the kanji down by theme:
五 means 5. It's read いつ, いつつ, or ゴ.
六 means 6. It's read む (e.g. む.つ, むっ.つ, むい), ロク, or リク.
臓 means entrails, viscera, or bowels. It's read はらわた or ゾウ.
腑 also means viscera or bowels. It's also read はらわた, or フ.
So let's take a closer look at 臓 and 腑. They both mean guts, they're both read はらわた, and they both use the radical meat-moon ⺼, plus (as you may have noticed if you're an absolute genius) another kanji that can mean storehouse. Yes!
蔵 means storehouse, or to possess, own, or hide. It’s read くら, おさ.める, かく.れる, ゾウ, or ソウ.
府 can mean storehouse, though it more often means urban prefecture or government office. It's read フ.
So, Flesh + Storehouse = Organs. Good mnemonic!
But is there a difference between 臓 and 腑? In modern Japanese, only 臓 is common, unless you're into traditional Chinese medicine. In that context, though, the difference is that 臟 zàng refers to "solid" organs, which are yin, while 腑 fǔ refers to "hollow" ones, which are yang. (Again, not organs in the anatomical sense; sometimes they're described instead as functional entities or systems.)
Anyway, I am going to try to end this post before I overstep my rudimentary understanding of this subject, but 五臓六腑 comes from the Chinese zàngfǔ (simplified: 脏腑; traditional: 臟腑). Zàngfǔ is the backbone of the TCM concept of how the body works. Its literal meaning is hollow and solid organs, or "all the organs."
And this kind of construction is common in kanji vocab: use two contrasting descriptors to refer to everything in a category or to position along a spectrum. For example:
男女 [だんじょ] (men + women) = all genders
老若 [ろうにゃく] (old + young) = all ages
大小 [だいしょう] (big + small) = size; all sizes
凸凹 [でこぼこ] (convex + concave) = bumpy
加減 [かげん] (increase + decrease) = adjust, moderate
苦楽 [くらく] (pleasure + pain) = the good and bad (of life)
高弱 [こうじゃく] (strong + weak) = level of strength
好き嫌い [すきぎらい] (like + dislike) = preferences (usu. food)
and so on.
P.S. - Incidentally, はらわた is more commonly written 腸. This character also shares the same general entrails/viscera meaning, but often refers more specifically to bowels/intestines. (And fun fact: The name 牛腸 Gochō (cow + bowels) was the impetus for me starting this blog!)
