(https://www.youtube.com/watch?v=sp3NKQlJPuo)[Link of the video!] I recently watched some gameplay from the Ubisoft game "For honor" and at some point the knight goes like "Oh f*** it" and starts attacking with the handle of his(or hers who knows) while holding it from the blade!
Gripping the blade was called half-swording, and it was actually done in real life.
One of the things that people often overlook when imagining combat between knights is that swords can not slash through nor normally penetrate through plate armour. As such, more creative ways of using the sword were required. One could grip the blade to have better control over the point of the sword, or one could indeed strike with the hilt of the sword instead of the blade, like some form of mace. Swords could also assist in grappling with the opponent.
Those particular images are from [a medieval manuscript](http://wiktenauer.com/wiki/Talhoffer_Fechtbuch_(MS_XIX.17-3%29) by the fencing instructor Hans Talhoffer. Half-swording appears in other manuscripts as well, and seems to have been common.
I might be wrong, but I believe OP is referring not to half-swording in general but to the murderstroke (mordslag) specifically, as shown in picture 11-12 of this 1522 armored fighting manual: http://wiktenauer.com/wiki/J%C3%B6rg_Wilhalm_Hutter/Armored_fencing.
Here is a youtube video demonstrating performing the murderstroke with a sharp sword and without any gloves.
The murderstroke was intended to attack a heavily armored opponent, as a sword is virtually useless against plate armor when used in the conventional way, as also neatly demontrated in this video. By using the sword like this, you essentially turn it into a hammer, enabling you to concuss your armored opponent.
