Sports matches played for practice or entertainment without official competition points; or military forces that are on your side.
From 'friendly' (from Old English 'freond' related to free, and the '-ly' suffix), pluralized to 'friendlies' in sports and military contexts, developing specialized meanings in the 20th century.
In military terminology, 'friendlies' is a chilling euphemism for 'our forces' that creates psychological distance—it's easier to coordinate around 'friendlies' and 'hostiles' than constantly saying 'our soldiers' and 'enemy soldiers.' Soccer/football culture borrowed 'friendlies' to mean low-stakes games, showing how language spreads from military to sports to everyday speech.
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