So what does Miroku's name mean then? Well, Miroku refers to the Maitreya (Miroku's name in sanskrit), the Buddha of the future, who also happens to be known as Jishi, Bosatsu of Compassion in Japan. In sanskrit, Maitreya's name means "loving one" in both sanskrit and japanese. Maitreya is the fifth Buddha and is also the most popular Buddha in the Early Heian period (794 to 894 AD). Coincidentally, Maitreya also happens to be a very popular subject of Japanese art.
According to the Shingon sect of esoteric Buddhism, Maitreya will will come down to Earth in the future and save all of those who are unable to be saved. To this day, the people of the Shingon sect await Maitreya's return, which should happen in 5.67 billion years.
A common misconception is that Maitreya takes on the form of the fat-bellied Buddha which one rubs the belly of for good luck. This is not the case as, apparently, many experts have concurred that Maitreya appears to be a slender, well-built man (or boy in some cases). The fat-bellied Buddha is an entirely separate entity!
Takahashi Rumiko made a rather clever move in naming Miroku after the fifth Buddha. The obvious similarity is that Miroku is a Buddhist monk and naming him after an actual Buddha seems like a logical thing to do. Buddhas are generally thought to be selfless, wise and calm. They are enlightened beings who can see clearly the world around them. Miroku may show various traits that lean towards being greedy, he has done many selfless things. Countless times he has risked his own life by using the kazana to save his friends and he's always willing to put aside his own quest and troubles to help those in need. Miroku is also calm -- he rarely jumps into situations without thinking them through and unlike Inuyasha, Miroku is patient and will take the time required to formulate a plan of action. He also rarely gets flustered in various situations, always keeping a level head.
Miroku is also wise. He knows much about youkai and how to defeat them as well as various other methods. He's also given Inuyasha plenty of advice when it comes to dealing with Kagome and Kikyou and his way of thinking before acting also shows not only his calmness but his wisdom too. He seems to have a wise air around him, making him an excellent person to talk to when advice is needed. Aside from personality traits, Miroku also seems to share Maitreya's description of being a slender, well-built man.