April has two possibilities. Some think it comes from aperire, a Latin word meaning “to open,” since April brings the opening of buds and flowers in the spring. Others think April was named after the goddess of love, Aphrodite, who was Mars’ consort.
May is named for Maia, an earth goddess of growing things.
June has apparently always been a popular time for weddings. The ancient Romans accordingly named this month after Juno, the queen of the gods and the patroness of weddings and of marriage.
July was named after Julius Caesar in 44 B.C. It was previously called Quintilus, the Latin word for “fifth,” since it was the fifth month in their calendar.
August is also named after a Roman Emperor: Caesar Augustus, who consolidated the Empire and established the “Pax Romana.” Prior to Augustus, this month was called Sextillia, meaning "six" (by now, I’m sure you can see the pattern).
September, October, November, and December come from the Latin words for seven (septem), eight (octo), nine (novem), and ten (decem).
In ancient Rome, the end of the year was marked by a huge festival called Februa. Around 690 B.C., Numa Pompilius (the second of seven kings said to have ruled Rome before it became a republic) made this festival a month of its own and named it February.
Later, this same Pompilius added another month to this time of the year, January, named for Janus, the god of beginnings and endings.