belch, vomit
噦 centers on the forceful expulsion of stomach contents: belching or vomiting. Both meanings share the idea of something rising and being ejected through the mouth.
噦 combines 口 (mouth) with 歲, which likely contributes a phonetic element. The exact historical development is uncertain, but the mouth radical clearly ties the character to oral actions like belching or vomiting.
The mouth 口 on the left and the complex 歲 on the right suggest something complicated happening in the mouth. Picture a mouth belching or vomiting with a noisy, messy sound.
For エツ, imagine the sound of a belch: a loud 'ets' escaping the mouth. The 'ets' sound cues エツ while the mouth component reinforces the belching action.