Roof radical on top, picturing a house with its sloping eaves. Anchors 宴 as something happening indoors and pairs the character with 家 home, 宿 lodging, 安 peace - banquets in old China were strictly hosted under one's own roof.
Lower 妟 (sun 日 over woman 女) supplies the yàn sound and a faint sense of 'peaceful repose'. Under a roof, the whole picture becomes a quiet indoor gathering - the relaxed feast that 宴 names.
