Flights of fancy and wit are great, but the landing can be a bit rough at times, and occasionally you draw flak. It helps to have a thick skin.
We may at first think of being thick-skinned as something that does not go together with cleverness. After all, to be clever, you need to be lithe, and burning with hot wit, yes? And thick skin is heavy and stiff. When someone’s really cracking wise or showing ingenuity, we say they’re on fire, and how can you be on fire if you’re all callused?
Well. You tell me how you can survive being on fire if you’re not. And if you’ve been on fire a few times and come out of it intact, I’m willing to bet your skin is not too thin.
This is why this word, callid, which means ‘crafty’ or ‘cunning’ (when it’s used at all, which is seldom anymore), does not trace to Latin calidus, ‘warm, hot, on fire’. No, it is from callidus, which means ‘clever, ingenious, crafty’ and – most to the point – ‘wise from experience’. And it is formed in turn from the verb callere, meaning ‘harden’. That root also gives us the (rarely used) noun and adjective callent, meaning ‘[one] knowledgeable or skilled in a particular area’ – and also the noun callus and the adjective callous.
We don’t think of a “callous” person as crafty or cunning, of course; we think of them as uncaring. And yet you can be said to be “thick-skinned” and still be likeable and thoughtful – and even caring. You are experienced to the point of being largely impervious to hurts to yourself, but you are not necessarily uncaring towards others. Funny how words that literally mean the same thing can have such different isotopes of sense.
And while callous humour is unpleasant and not really funny, people who are thick-skinned are more likely to be able to laugh at themselves, and to take risks and not be afraid of a bit of friction. A good and experienced cook probably has tough skin on skilled hands. What is calidus can thicken the skin and make it callidus. Wisdom means experience, means some amount of learned durability.
Look at it another way: we don’t really expect someone to be usefully quick-witted and inventive if they’re thin-skinned, do we?