To join the conversation; to unite in an effort; to contribute money.

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a. 1870.  

        Flynn of Virginia—
  Just you chip in,
  Say you knew Flynn;
Say that you’ve been ’yar.
F. Bret Harte, ‘In the Tunnel.’ (N.E.D.)    

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1888.  We refuse to chip in for a church, but will contribute $10 to help get Lampas Jake, the revivalist, down here.—Detroit Free Press, Oct. (Farmer).

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