tanned leather radical (no. 178)
韋 centers on tanned leather and the idea of processed animal hide. As a radical, it carries that leather sense into other characters.
韋 is thought to depict a foot (㐄) going around an enclosure (口), originally meaning to go against or oppose. Over time it came to be used for tanned leather, possibly through phonetic loan or semantic extension.
The bottom 㐄 looks like a stretched hide, and the 口 inside is like a frame for tanning. Picture a skin stretched on a frame to become tanned leather.
For イ, imagine an eagle (イーグル) swooping down to grab a piece of tanned leather: eagle -> イ, and the leather is carried away.