Entirely speculation here, but the name Voltimand appears to be of an anglicized French form. Like "Voldemort" comes from "vol de mort," meaning flight of death, I suspect "Voltimand" may be related to the word "Volte-face" and "main," meaning hand. Or it could be related to the ending in words such as "gourmand." My best guess? It somehow means "at-hand," as in, to be at the beck and call of, say, the king.
Discussion in comments warranted.