When you read the name "Ivanhoe," does it sound romantic and Old-English-y to you? We hope so, since that's what author Sir Walter Scott intended. In his 1830 introduction to a new edition of Ivanhoe, Scott stressed that he picked name for two reasons: first, because it sounds nice, and second, because it doesn't mean anything in particular.
"Ivanhoe" is a name filled with mystery. It could refer to anything: a place, a special sword, a recipe for grilled salmon – or all of the above. For Scott, it's the last name of Wilfred of Ivanhoe, the fictional hero of our novel. But you're not going to know that unless you open the book and read more to find out. By picking a name that looks good but means nothing, Scott is trying to lure you into buying the book and finding out, "Who, what, or where is this mysterious Ivanhoe?" Did he succeed? That's up to you to decide.
As for where Scott himself got the name, in his "Introduction" he mentions a childhood nursery rhyme:
Tring, Wing, and Ivanhoe,
For striking of a blow,
Hampden did forego,
And glad he could escape so.
This rhyme comes from an old story (probably not true) about Edward III – king of England from 1327 to 1377 – and his son Edmund, the Black Prince. The story goes that the king and the prince went to visit one of their lords at Great Hampden for some relaxation time. During a game of tennis, the prince and his host, de Hampden, got into a fistfight. De Hampden decked Prince Edmund in the face. King Edward III was so angry that one of his subjects would dare to strike his son that he left the hall at Great Hampden right away. To smooth things over with the royal family (and to keep his head from getting chopped off) de Hampden gave King Edward III three rich estates: Tring, Wing, and Ivanhoe (source). Scott thought the name "Ivanhoe" had a certain ring to it, so there you have it.