The supposed ability to detect underground water, metals, or other hidden things by walking over them; divining or dowsing-like practice.
From Bartholomew Bleton, an 18th-century French water-finder who claimed special sensitivity. The suffix '-ism' names a practice or system. Named practice faded from science but word remained.
A French peasant named Bleton convinced people he could find water by walking with a stick—so scientists named the practice after him! It's pseudoscience, but his name got immortalized in a technical term anyway, showing how one person's claim can become a vocabulary word.
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