sun-stroke
暍 centers on the harmful effect of extreme heat: sunstroke, a condition caused by overexposure to the sun.
暍 combines 日 (sun) with 曷, which likely contributes the sound and may relate to heat or exhaustion. The exact historical development of 曷 is uncertain.
The sun 日 on the left beats down on the right side 曷, which looks like a person wilting under a heavy load. Together they show sunstroke: the sun's heat overwhelming the body.
For エツ, imagine someone suffering sunstroke and gasping 'Ets!' as they collapse from the heat. The sharp sound 'Ets' cues エツ while the sun 日 reminds you of the cause.