Ferrule

A ferrule is a metal band or ring fitted around a tool handle at the point where a chisel, file, or similar tang-mounted blade enters the wood, reinforcing that spot against splitting. It matters most on struck tools -- a chisel driven with a mallet repeatedly puts real stress right at the handle's neck, exactly where a ferrule sits, and a chisel missing or with a cracked ferrule is a genuine candidate for the handle eventually splitting under that repeated impact.