Hard to pin down

Origin

The phrase "hard to pin down" conjures a vivid image, perhaps of a scientist trying to precisely classify a restless insect, or a wrestler struggling to hold an opponent still on the mat. This direct, physical sense of trying to immobilize something, to fix its position or nature, gradually broadened into a powerful metaphor. By the 20th century, the struggle to physically pin something down had evolved into a linguistic tool for describing the mental challenge of comprehending something abstract or getting a definitive answer from someone evasive. It's the frustration of an idea that refuses to be neatly categorized, or a person who constantly shifts their stance, leaving you perpetually grasping at air.