David Brooke says in 'The Railway Navvy; that despicable race of men' that Pincher was a term for an experineced navvy. The Oxford english dictionary says that a rare usage of pincher is for one who uses a crowbar to move rock and cites a usage from 1855. Tregelles says in 'the ways of the line', 1858 that 'the navvy proper deals only with the shovel, the pick, the crowbar, and the wheelbarrow'