A tool with jaws used to grip and turn nuts and bolts (called a wrench in American English), or something that disrupts plans (as in 'throw a spanner in the works').
From German 'Spanner' meaning one who spans or grips, from 'spannen' (to stretch or grip). The word entered English from German engineering terminology.
When we say 'throw a spanner in the works,' we're picturing a saboteur literally throwing a tool into machinery to break it—and this actually happened during labor disputes and wars, making the expression vivid and historically grounded!
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