1. The age of 70, which has been rare since ancient times, is called seventy years of age. It is precisely because in ancient times, because the average age of people is not very long, it is very rare to have a 70-year-old man, which is called the age that has been rare since ancient times, so it was called seventy years of age by people at that time. Although many people regard seventy years of age as a fixed name, they don't quite understand the real meaning. In the literal meaning, we can understand what its real meaning is, and of course it is also a kind of hope for the elderly.
Second, the abbreviation of the approximate meaning Although 80 years old is called the octogenarian, the octogenarian refers to the elderly between 80 and 90 years old. The octogenarian refers to the 70-year-old man, and the octogenarian is not only the 80-year-old man, but the older man. After all, in ancient times, it was rare to see the 80-year-old and 90-year-old man. That's why there is such a general term, not just 80 years old. Nowadays, many people don't quite understand the correct meaning, but now it seems very easy to understand.
The ancients had a certain abbreviation for age, of course, in order to make everyone more aware of their age, so they had such a title when introducing them. For today's people, they rarely have such a title, but in ancient times it was a very humble way to tell the age directly, which may show disrespect, so they had such a title at that time, and now it is also to show respect for the elderly.