When the crew of Lewis Carroll’s The Hunting of the Snark is making preparations for seeking that impossible creature, we read that “the Boots and the Broker were sharpening a spade”. This action is so outlandish that the editor and commentator Martin Gardner remarks ad locum: “Why in the world were they sharpening a spade?” (Gardner 2006: 44.)
Sharpening a spade is not outlandish. I saw farmers and gardeners doing that. Sharpening the spade before digging makes work easier. I think that Gardener simply asked what the Boots and the Broker wanted to do with a spade.
Quite probably the Boots and the Broker sharpened a spade because they were going to dig.