Grandson, originally referring to the daughter's children, now refers to the daughter's son, also known as "grandson". And grandson generally refers to the son of a son, so grandson and grandson are relative words, so grandson and grandson are different.
Grandchildren and grandchildren belong to kinship terms, but there is no way to verify when kinship terms began. As far as the information we can see today is concerned, there have been relatively systematic kinship terms in Oracle Bone Inscriptions. The number of kinship terms in Chinese: There are 1800 categories of "family and relatives" in the Encyclopedia of Ancient and Modern Appellations in China. The Dictionary of Kinship Appellations contains 3,500 kinship terms, including ancient appellations and modern dialect appellations.