carry, contain, load
儎 centers on the act of transporting or holding something: carrying, loading, or containing items. The meanings all relate to moving or supporting a burden.
儎 is a phono-semantic compound: the person radical 亻 (person) suggests human action, while 載 (carry, load) provides both sound and meaning. The character likely developed as a specialized variant emphasizing a person carrying or loading.
A person 亻 beside 載 (which itself means carry or load) visually reinforces the idea of a person carrying or loading something.
For サイ, imagine a person loading a heavy sigh (サイ) onto a cart: the sigh sound cues サイ while the person carries the burden.