Scrum, the set of practices in Agile project management that emphasize daily communication and flexibility, takes its name from a formation in the sport of rugby.
The term scrum was first introduced by Hirotaka Takeuchi and Ikujiro Nonaka in their 'The New New Product Development Game' research paper in 1986, specifically in a section headed "Moving the scrum downfield". They apparently chose the word because they felt it stressed the importance of working as a team to achieve a goal.
In rugby a scrum involves eight players from each team interlocking heads and pushing with all of their strength to move the opposing team backwards. Rugby was created in 1823 and there's evidence the term scrum was used in this sporting context from at least the 1870s onwards.
Sources: The New New Product Development Game