Is Gordon Ramsay right to use the term "plank" for an "idiot"?
In this video clip, amateur reality TV-chef Gordon Ramsay says,
I think you're a plank. [...] Plank means an idiot.
Is this a real definition of plank? Dictionary.com doesn't acknowledge it. Is Gordon Ramsay just calling people a slice of a dead tree?
From “15 Ways Of Saying 'Idiot' In Ireland, Ranked In Order Of Stupidity”:
Plank Implying someone's has a thick head, more skull than brain.
From BBC.co.uk
Plank:
Literally, a plank is a piece of wood often used in the construction industry. There's an expression in English 'as thick as two short planks' which is a negative term for someone who's really unintelligent. Don’t ask me why short planks might be thicker than long ones, that's just what we say.
Well, we've been saying that idiots are as thick as two short planks for a long time, but recently this has been shortened and now, if we think someone isn't very bright, we just called them a plank. We might say, 'You'll never guess what he said to her, he's such a plank!'
........
We’ve been using the association with wood in a negative sense for a long time. A wooden actor, is a useless, unable to express emotion. So if someone does something unbelievably silly, you might just quietly say to yourself 'What a plank!'
Jonathon Green,Chambers Slang Dictionary (2008) has this entry for plank in the relevant sense:
plank n. {S[tandard] E[nglish] plank, both lit.and fig. uses based on ...TWO SHORT PLANKS under THICK AS... adj.} 1 {1960s+} (Aus[tralian]) a surf board. 2 {1980s+} (also plankbrain) a fool. ...
Under the multipart thick as... entry, Green has this:
...two short planks (also thick as eight short planks, ...two bricks) {1970s+} very stupid.
Tony Thorne, The Dictionary of Contemporary Slang (1990) identifies plank in this sense as specific to British English:
plank 1 British a dull-witted person, someone who is as 'thick as two short planks'.
Eric Partridge & Paul Beale, A Dictionary of Slang and Unconventional English, eighth edition (1984) dates the "as thick as two short planks" source language to the early 1950s in this entry for the related adjective planky:
planky. Dull-witted; stupid: evolved. ca. 1955, ex '(as) thick as two short planks': Services'; later, more widespread.
and in this mention in the entry for "thick as ..., as":
The increasing use of thick, adj., in C.20 has produced many variations on Falstaff's simile [in Henry the Fourth, Part 2: "his wit is as thick as Tewksbury mustard"]; a few are: as two short planks: orig. Service' since ca. 1950, > more widespread, and since ca. 1970 giving rise to elliptical planky; ...
So plank in the sense of "dullard" seems to have originated in the 1970s as an offshoot of "as thick as two planks," which arose in the British military services in the early 1950s as a particular instance of the "as thick as" family of similes (all meaning "as dull as") that goes back at least as far as Shakespeare.