Posted by The Carpenter on April 23, 2000
In Reply to: Origin of phrase 'as thick as...' posted by pip kirby on April 22, 2000
: can anyone tell me the origin of or sense in the phrase'as thick as two short planks? Why two planks and why short?
The perceived thickness of a plank depends on its length. Consider a plank of length 25ft which is, say, 6" in width and .1" in thickness. Now by any estimation that's one thin plank. Now consider the same plank but this time we'll take a saw to it and reduce its length to 0.2", its width to 0.15" but we'll leave the thickness at .1". So now what to we have? We have a very short plank - some might even say "is it a plank at all?" - but it is a plank and, relatively speaking, a very thick short plank. Now consider that you have two of these planks, plonked, one on top of the other. Then what do you have? You have a pile of wood (oh, didn't I say, the planks are made of oak in this case; seasoned oak) which is 0.15" wide, 0.2" long and 0.2" thick. I think, that by any definition, that's real thick. Hence the phrase 'as thick as two short planks.
Given the display of erudition above you'll be dismayed to learn that I have not the faintest idea as to why the expression 'as thick as two short planks' has come to mean of low intelligence. Nor do I have the faintest notion as to where it was first used, or by whom.
I avoid using the expression myself as it tends to offend those who are not and isn't understood by those who are.