the.com/friendly fire

means Injury or damage inflicted by your own side's weapons rather than the enemy's — the accident of war that comes from chaos, bad coordinates, or mistaken identity, not malice.

from Military jargon from the 20th century, built simply from 'friendly,' meaning allied forces or one's own side, paired grimly with 'fire' as in weapons fire. The phrase likely hardened into common use around the World Wars and especially Vietnam, where confusion on the battlefield made mistaken attacks on one's own troops common enough to need a tidy euphemism. The irony of pairing 'friendly' with being shot is the whole point — language softening a brutal, unglamorous reality of combat.