The origin of the saying ‘upper crust’ to mean the aristocracy is said by some to have come from the fact that only the well-off were given the upper crust of a loaf. (Because of the style of early ovens the bottom of the loaf would tend to be burned by comparison with the top.) There is no written evidence for this usage. Another idea is that pies for the nobility had an upper crust whereas the poor could only afford one layer of pastry – the one underneath the contents. Again there is no written evidence for this origin.
However, the idea of the head being referred to as the upper crust does appear in print as early as 1823 when Grose's Classical Dictionary of the Vulgar Tongue said – “...but to hear it from the chaffer [mouth] of a rough and ready costard-monger, ogling his poll from her walker [feet] to her upper crust [head].”
It is therefore quite likely that this was simply extended to suggest those at the top / head of the social strata.
"The upper crust seem to think bad manners are of no account."
