Every authority I've read on the works of William Shakespeare agrees that what the great man probably meant when he had Hamlet say that he knew a hawk from a handsaw, was the Dane knew a hawk from its prey, the heronshaw, hansa, harnser, or (grey) heron. The only person I have ever heard casting a doubt on this was a friend of mine from Warwickshire, who told me that handsaw, for heronshaw, has never been recorded in her county, and that Shakespeare, the countryman, would have used a dialect word such as those I have given above. Eoin O Cofaigh, architect, indeed president of the Royal Institute of his profession, wrote to me to say that he doesn't agree with the decision of the great dictionaries either. He is worth listening to.
A hawk, he points out, is a name for a plasterer's or mason's mortarboard, and the word is still used in the trade. Shakespeare was talking a working-man's language: a country boy who also knew the tradesmen of a great city would have no difficulty in distinguishing between two of the most common of craftmen's tools.
The problem here is the lexicographer's perennial one of dating words: how old is hawk, meaning a plasterer's mortarboard? Well, it is quoted in a tract on building by a man named Moxon in 1700: `Tools relating to Plastering: A Hawke, made of Wood about the bigness of a square Trencher, with a handle, whereon the Lime and Hair being put, they take from it more or less as they please.'
Did Shakespeare know the word a century earlier? Yes, I'd say. Tradesmen are the most conservative of people when it comes to words. I notice, too, that no other instances of the phrase, other than the quotation from Shakespeare, have been found. To me, Mr O Cofaigh's gloss is perfectly plausible, and I've taken the liberty of sending it to both Oxford and Collins. I hope it doesn't end up as my glosses on pet and tally ho did, in somebody's wastepaper basket.
John Joe Smyth, of Willow Grove, Delgany, a master carpenter, tells me that a hawk is also a mason's labourer in parts of England: the fellow who carries the hod. I assume that this is where the verb to hawk, to carry anything about with labour, comes from.
A hawk is also a cataract on a Wexford horse's eye. The origin of all these hawks? A mystery, I'm afraid.