salted meat
醢 centers on meat preserved with salt, specifically salted meat or a fermented meat paste. It is a rare, specialized kanji for an ancient food preparation method.
醢 combines 酉 (a jar or vessel for fermentation) with a right side that likely relates to meat or preparation. The exact historical development of the right component is uncertain, but the character as a whole represents salted or fermented meat stored in a jar.
The left side 酉 is a sake jar, suggesting fermentation. Picture a jar packed with meat and salt, left to ferment into a savory paste: that's 醢, salted meat.
For カイ, imagine a jar of salted meat so pungent it makes you cry out 'KAI!' as you open it. The sharp sound 'KAI' matches the reading and the strong preserved flavor.
salted flesh (fish, etc.)