eunuch
閹 centers on a eunuch, a castrated man historically employed as a palace attendant or guard. The meaning is specific and does not extend to broader abstract ideas.
閹 combines 門 (gate) with 奄, which likely contributes the sound and relates to covering or enclosing. The character originally referred to a castrated gatekeeper or palace attendant.
Inside the gate 門, the component 奄 suggests a person who is enclosed or kept within the palace. Picture a eunuch standing guard just inside the gate.
For エン, imagine the eunuch at the gate saying 'Enter' in a formal tone: 'Enter' -> エン, and he lets you through the gate.