Wiktionary
twibill
n. 1 An axe with two cutting blades 2 A mattock 3 A double bladed tool used in gate type hurdle making for cutting out mortices, with a flat chisel and a mortice chisel or hook, similar to the much larger french carpenter's tool, the bisaigue (or besaigue) 4 (context obsolete English) A double-bladed halberd or battle-axe