Collective wisdom would have it that sailors in the Royal Navy were served their meals on square plates (or trenchers – hence trenchermen) that would be more stable in rough seas, particularly between meals when they might be in racks.
This, it is said, is the origin of “three square meals a day” and indeed this might well be the case, but there is no written evidence of this origin despite extensive naval records.
Incidentally, the ridge around the outside of the plate or trencher was known as the ‘fiddle’ so someone who was getting more than a fair share was said to be ‘on the fiddle’.
A more likely explanation for a square meal is that, in Masonic terms, if something is fair and honest it is said to be ‘square’ – hence ‘fair and square’.
Freemasons are well known for dining well after their meetings, and so the connotation of a ‘square meal’ could well have come from this.