The title, Arms and the Man, is an ironic reference to Virgil's Aeneid, which glorifies the warrior. Shaw's play, in contrast, satirizes the idea of the warrior hero, showing Sergius as an incompetent who has blundered into heroism by mistake, and, also reveals that Sergius, despite his highly romanticized wooing of Raina, is, in actuality, seducing her servant Louka.
Therefore, the real "man" in the play is not the supposed warrior hero Sergius, but the pragmatic Bluntschli who deserts the battlefield and show up at Raina's balcony. Bluntshcli does not fall for false romanticism, be it in love or war, and it is he who wins Raina in the end. In the last line of the play, Sergius says of Bluntshli, "What a man! What a man!" Sergius still doesn't understand Bluntschli, but the repetition of "man" in the last lines emphasizes that Bluntshcli is the real man in the play.
"Arms" means weapons of warfare, but it is also a play on the kind of possessive love embodied in the idea of folding a beloved in one's arms as a conquest. Sergius, in particular, tends to gather Louka in his arms as an object he owns. When she questions whether his statement that she "belongs" to him is an "insult," he responds: "It means that you love me, and that I have had you here in my arms." Shaw critiques this idea of love as ownership.
The title of Arms and the Man by George Bernard Shaw is based on the opening line of Virgil's Aeneid,
Arma virumque cano, Troiae qui primus ab oris Italiam, fato profugus
I sing of arms and a man who first, exiled by fate, [came] from the shores of Troy
This line begins a great epic telling of the heroic deeds of Aeneas, who fled after the fall of Troy in the Trojan war to found Rome.
The purpose of the title is to give us a different take on warfare. Captain Bluntschli is also fleeing after losing a battle, but rather than being a heroic character about to found a great empire, he is a rather pragmatic, bourgeois mercenary, who is quite happy to abandon warfare for running a hotel chain when he has the opportunity to do so. In his meeting with Raina, which parallels Aeneas' meeting with Dido, Bluntschli is more concerned with obtaining food and getting some sleep than with glory.
What this does is locate the play in a "mock epic" tradition, which evokes the grand and hyperbolic traditions of heroic epics only to satirize and deflate them.
As explained by George Bernard Shaw in his preface to the play Arms and the Man, in choose this title of the play based on the first line of famous ancient epic Aeneid by Virgil - that is "I sing of Arms and the Man".
However the thoughts and feeling expressed by Bernard Shaw are quite opposite of those of Virgil.
Arms and the Man by Bernard Shaw is a satire in the practice of romanticizing war and reckless heroism in war. He is trying to tell the readers that best soldiers are very piratical in their approach to war. They are not swayed by emotions such as heroism and fearlessness. They act on the basis to cold considerations of their chances of success.