Sort lists allow you to type one piece of information in a cell, then drag it to fill in a consecutive list of items.
For example, enter the text "Jan" or "January" in an empty cell. Select the cell and click the mouse on the lower right corner of the cell border. Then drag the selected cell a few cells to the right or downwards. When you release the mouse button, the highlighted cells will be filled with the names of the months.
Hold down CommandCtrl if you do not want to fill the cells with different values.
The predefined series can be found under LibreOffice - PreferencesTools - Options - LibreOffice Calc - Sort Lists. You can also create your own lists of text strings tailored to your needs, such as a list of your company's branch offices. When you use the information in these lists later (for example, as headings), just enter the first name in the list and expand the entry by dragging it with your mouse.