1
general::
Last in sequence but not least in importance, as in Last but not least, I want to thank all the people who sent me copies of my article in the paper. [Late 1500s]
American Heritage Idioms
2
general::
Phrase(s): last but not least
Cliché last in sequence, but not last in importance. (Often said when introducing people.) • The speaker said, "And now, last but not least, I’d like to present Bill Smith, who will give us some final words." • And last but not least, here is the final graduate.
McGrawhill's American Idioms And Phrasal Verbs