In British slang, a "spanner" is used to describe a foolish or clumsy person. The term likely stems from the tool known as a spanner, which is the British equivalent of a wrench in American English. Over time, "spanner" became a metaphor for someone who might metaphorically "throw a spanner in the works," causing disruption or making a situation more difficult. This expression highlights the British penchant for using everyday objects to create vivid and sometimes humorous slang. The term is often used in a playful or teasing manner, underscoring the rich tapestry of British colloquialisms that make everyday language vibrant and engaging.