thick, strong
靁 centers on something dense and forceful: thick in substance or strong in intensity. The given meanings describe a concentrated, powerful quality.
靁 is an ancient variant of 雷 (thunder). It combines 雨 (rain) with three 田 (fields), likely emphasizing the rumbling, repetitive nature of thunder. The modern meanings 'thick, strong' may derive from the idea of dense, powerful thunderclouds.
Rain 雨 pours down over three stacked fields 畾, making the soil thick and heavy. The scene feels dense and strong.
For ライ, imagine a thick, strong lie (as in a false statement) rumbling like thunder: lie -> ライ, and the dense clouds make the lie feel heavy.