Cannot Add Named Ranges Any More

I have a large Excel XLSM workbook that contains multiple modules, over 100 worksheets, and many named ranges (maybe over 100). I need to add more named ranges in order to complete the next level of programming. However, Excel won't let me add anymore. When I type the name in the name box, it won't stick. I did some research and found out that the number of named ranges I could create was only limited by memory.

So my question is: what specific memory is Microsoft referring to? Is it the RAM on my computer or something else? How do I recycle some of the memory in order to be able to add named ranges again?

Thanks so much!