The Collaborative International Dictionary of English v.0.48:
But \But\, n. [See 1st But.] 1. A limit; a boundary. [1913 Webster] 2. The end; esp. the larger or thicker end, or the blunt, in distinction from the sharp, end. Now disused in this sense, being replaced by butt[2]. See 1st Butt. [1913 Webster +PJC] But end, the larger or thicker end; as, the but end of a log; the but end of a musket. See Butt, n. [1913 Webster]