to be on short commons

Commons \Com"mons\, n. pl.,
   1. The mass of the people, as distinguished from the titled
      classes or nobility; the commonalty; the common people.
      [Eng.]
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            'T is like the commons, rude unpolished hinds,
            Could send such message to their sovereign. --Shak.
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            The word commons in its present ordinary
            signification comprises all the people who are under
            the rank of peers.                    --Blackstone.
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   2. The House of Commons, or lower house of the British
      Parliament, consisting of representatives elected by the
      qualified voters of counties, boroughs, and universities.
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            It is agreed that the Commons were no part of the
            great council till some ages after the Conquest.
                                                  --Hume.
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   3. Provisions; food; fare, -- as that provided at a common
      table in colleges and universities.
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            Their commons, though but coarse, were nothing
            scant.                                --Dryden.
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   4. A club or association for boarding at a common table, as
      in a college, the members sharing the expenses equally;
      as, to board in commons.
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   5. A common; public pasture ground.
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            To shake his ears, and graze in commons. --Shak.
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   {Doctors' Commons}, a place near St. Paul's Churchyard in
      London where the doctors of civil law used to common
      together, and where were the ecclesiastical and admiralty
      courts and offices having jurisdiction of marriage
      licenses, divorces, registration of wills, etc.

   {To be on short commons}, to have a small allowance of food.
      [Colloq.]
      [1913 Webster] Common sense