A village in County Cork, Ireland, near Cape Clear. This is just about as far southwest as you can go in Ireland and not fall into the Atlantic Ocean.
It is unclear how George Calvert, the first Lord Baltimore, came to take the name of this tiny, remote place as part of his title. There is really no evidence to associate any Calvert with Cork; Calvert lands in Ireland were in Counties Longford and Wexford. Since Calvert was given the title in 1625 when he resigned from the Privy Council in protest of anti-Catholic legislation being considered by Parliament, I once thought that this was a joke on his part, or at his expense. However, now, it appears that he derived his title from the name of his estate near Cloonageeher in County Longford. So, it may be that Charm City and the tiny fishing village in County Cork have the same name entirely by coincidence.
A remnant of my writeup here, now moved to Baltimore, Maryland.
Update, 1/27/2003: ReiToei says "Baltimore is made up from three words, baile, tigh, mor, meaning town, house, big, or 'Town of the Big House'". But I've also heard theories that the first syllable comes from Baal meaning a place of idol-worshipers.