eclipse, occultation, be defective
蝕 centers on the idea of something being gradually eaten away or obscured: an eclipse where a celestial body is hidden, or a defect that slowly erodes integrity.
蝕 combines 食 (eat) with 虫 (insect/worm), suggesting something being eaten away like a worm consuming food. The eclipse sense likely extends from the idea of a celestial body being 'eaten' or obscured.
A worm (虫) is eating (食) away at something, causing it to be defective or obscured—like an eclipse where the sun or moon is gradually consumed.
For ショク, imagine a shock (ショック) when you see a worm eating your food during an eclipse: shock -> ショク.