The phrase "last but not least" is used to introduce the final item in a list of people or things, emphasizing that this final item is just as important as the ones mentioned before it. It serves to highlight that even though it is being mentioned last, it should not be considered less significant.
The phrase "last but not least" has its origins in English, where "last" refers to the end of a sequence, and "not least" emphasizes that the preceding item maintains a level of importance. This construction has roots in similar figurative expressions from classical literature, emphasizing inclusion despite order.