to hide, to secrete, to repress, to bend
匽 centers on concealing or suppressing something: hiding it away, keeping it secret, or holding it down. The bending sense is a physical extension of pressing something out of sight.
匽 combines the enclosure 匚 with 妟 (日 over 女). The exact historical development is uncertain, but the structure likely suggests something hidden or bent within a container.
Inside the box 匚, a woman 女 is hidden under the sun 日, as if bending down to stay out of sight. The whole scene means hiding or repressing.
For エン, imagine the hidden woman bending to end her concealment: end -> エン, and she finally stops hiding.