Where does the term "hand-and-a-half sword" come from?

It is a sword that is a bit longer than a one-handed sword, and shorter than a two-handed sword. It is light enough and maneuverable enough to be used with one hand, but with a long enough handle to use two hands for very powerful cuts.

It was sometimes called a bastard sword, since it was neither a one-handed nor a two-handed sword, and also called a hand-and-a-half sword for the same reason.

From quckly looking a couple of sources from this wiki article it looks like it's translated from an italian term for these swords, which were generally called bastard swords in the past. The article itself says the "hand and a half" term started being used in the late 19th century but I don't see where that's substantiated. I guess "hand and a half" sounded better than "bastard" to some people.

http://en.wikipedia.org/wiki/Longsword#cite_note-7

The term of course refers to the fact that the sword can be used one handed, or with the second hand on the pommel in a sort of two handed grip

One day,in a village far,far away,a long,long time ago, a young farm boy went into the field to collect some wheat. When he was in the field,one of the great king's soldiers ran through the field shouting "RUN FOR YOUR LIFE!". The young man harvesting wheat jumped out of the way just in time to avoid being trampled by the soldier. When the boy stood up, he saw a giant lion chasing the soldier. Suddenly,the lion stopped and stared at the boy. The wild animal stood on its hind legs and let out a ground shaking roar,so powerful that the boy could see the soldier fall in the background. The boy fell on his bottom,and then stood bay up as quickly as possible. The lion leaped at the boy,but the boy was able to leap out of the way just in time. The boy then scrambled to his feet and grabbed his harvesting sickle. The boy sprinted to the fallen soldier with the lion snapping at his heels. Then, the lion pounced on the fallen soldier and a brilliant blue-white light shot from his mouth and went straight into the soldiers heart,suddenly,the soldiers body went limp. He had passed. In a desperate attempt to save the soldier,the boy grabbed his sickle and swung it at the lion,but missed repeatedly. The lion jumped at the boy and clenched its fangs onto the boys left arm,and then all the way from the boys fingertips to his elbow glowed an eerie blue light then vanished. In terror,the boy swung on his heels and ran back inside his hut. Out the window,the boy could see the lion waiting for him to return so that the animal could feast once more. After the third day of waiting,the lion gave up and went back into the forest. As soon as the lion was out of view,the boy rushed out into the field and grabbed the soldier and the boy tried to drag him inside his house. But,to the boys surprise,the soldier was stuck to the ground. As the boy was desperately tugging on the man's arm,the soldiers sword came loose and landed on the ground before the boy. Acting on instinct,the boy quickly grabbed the sword and his sickle and dashed back inside. That night,during supper,the boy realized that he could not possibly fight the lion with this sword,as it was too short,he would certainly miss and get his other hand bitten off. So,the boy set straight to work,making a mold for a new sword. He worked day and night,pounding the mold into shape. When the mold was finished,it was the shape of a very long sword. The boy put the passed soldiers sword into the mold so that he may see how much remaining metal he needed. After the sword was fit into the mold,the boy put his hands into the extra space and saw that he needed a hand and a half of metal. the boy then detached the metal off of his sickle,melted it down along with the sword,and molded them together. After two days in the fire and one day of cooling,the boy removed the brand new sword from its mold and pointed it skyward. "I'll call it, the hand and a half sword!" He shouted to the heavens. The boy kicked open the door and pointed the sword in front of him. The lion suddenly charged out of the forest and roared a ferocious roar,the boy shouted back at the lion and then slayed the lion.

Thus,the birth of the term "Hand-and-a-half sword". In the later stages of humanity,it was renamed the longsword because it was much more simple to say.

Have a great day! Hope that I could help!