The entrenchment tool was originally given to soldiers on both sides of the conflict as a utilitarian tool for digging trenches or graves. Soon combatants found them to be useful in close quarters combat as a melee weapon. In no time at all troops on both sides were sharpening their shovels and wielding them like swords.
The game is Battlefield 1 Team Deathmatch. Map: St. Quentin Scar. This video contains multiple demonstrations of shovel kills in Battlefield 1 along with expert commentary from Willy Mammoth.