entangle, entwine, coil
縈 centers on things wrapping around each other in a tangled way: entangling, entwining, or coiling together.
縈 combines 糸 (thread) with a phonetic element historically related to 熒 (a flickering flame shape). The thread component suggests entanglement, while the upper part likely contributed the sound.
The bottom 糸 is thread, and the upper part looks like a tangled mess of lines around a fire. Picture threads wrapping and coiling around each other until they are completely entangled.
For エイ, imagine an 'A'-shaped coil of thread that entangles everything: the letter 'A' sounds like エイ, and the thread forms an 'A' as it coils.