From Wiktionary, the free dictionary
Sino-Vietnamese word from 次女, composed of 次 (“next”) and 女 (“female”).
thứ nữ
- (formal, chiefly on wedding invitation cards or at weddings) the second, but not youngest, daughter
- Coordinate terms: ái nữ, quý nam, quý nữ, thứ nam, trưởng nam, trưởng nữ, út nam, út nữ