Masks; much ado about noting
The title of Shakespeare's work, which in part reflects a flippancy adopted by Shakespeare in naming of the comedies he wrote around the same time (As You Like It and Twelfth Night, or What You Will), also puns on the pronunciation of the word "nothing," which sounded like "noting" in Elizabethan English.
The play focuses in many ways upon characters "noting" one another. Perhaps most important is Claudio's mis-noting of Hero, which persuades him to spurn her at the altar. The prevalence of masks also reinforces the importance of characters noting each others' identities. Thus, in the masked party scene, which relates to the Elizabethan formal masque, Beatrice is able to speak to Benedick as though he were someone else, giving Beatrice a good chance to be insulting to him and leaving Benedick believing that she did not recognize him.