Shamino, as an Ultima character, has a real-life counterpart: Richard Garriott, the designer of the series. (He's also in the game as Lord British, a part of which he's more known for - the father of the series gets two roles, other responsible people only one =) Actually, Garriott in real life looks a lot more like Shamino than old and wise LB...
There has been some speculation on where the name came from. The facts, as we know them, are that Garriott used the name in SCA - so apparently it is a medieval-era name. Some say the name occurred to him when he misread his bicycle's gear shift manufacturer name (Shimano). Some say it's related to a "biking accident".