This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
婇 combines 女 (woman) with 采, which may have contributed sound. The exact historical development is uncertain.
A woman 女 beside 采, a shape associated with picking or gathering. Without a clear meaning, picture a woman gathering something unknown.
For サイ, imagine a sighing woman: sigh -> サイ, but the meaning remains unclear.