In one's corner

Origin

In the brutal world of prize fighting, particularly boxing matches that gained widespread popularity in the 19th century, each combatant was assigned a specific corner of the ring. Here, their seconds, trainers, and coaches would gather between rounds, offering critical advice, tending to injuries, and providing much-needed encouragement. These individuals were literally and figuratively 'in the fighter's corner,' dedicated to their success against an opponent. This vivid image of steadfast support in a confrontational arena readily transitioned into everyday language, evolving to describe anyone who stands by another person, advocating for them and providing solidarity when it's most crucial.