Shemini Atzeret directly follows Sukkot, which is celebrated for seven days. It is a separate yet connected holy day devoted to the spiritual aspects of the festival of Sukkot. 

We don't know exactly what atzeret means. It may come from the word atzar, meaning “stop,” implying that we are to stop, or refrain, from work. Atzeret may also be defined as a deliberate extension of the prior seven days. The lack of verbal clarity may be why the rabbinic sages seemed to struggle with the precise meaning of the holiday.

Samson Raphael Hirsch, a 19th-century Orthodox rabbi who lived in Germany, infers the meaning of the holiday from the word atzeret, which he interprets as “to gather” or “to store up.” On the eighth day of Sukkot, we must gather the gratitude and devotion we have acquired during the days before Sukkot.