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The lyrics are at least as old as 1832 where they appear on a broadside but there were already several versions by that date. The tune is the Lincolnshire Poacher.
There is a good a capella (with bodhran) version by the Kilkennys.

    Chandler's Wife, The

    by trad
    As [G] I walked into the chandler’s shop some [D] candles for to [G] buy,
    I [G] looked around the chandler’s shop but [Em] no one [Am] did I [D7] spy.
    [G] I was disappointed and some [D] angry words I [G] said,
    When I [G] heard the sound of a KNOCK KNOCK KNOCK [F] up above my [G] head.
    When I [G] heard the sound of a KNOCK KNOCK KNOCK [F] up above my [G] head.

    I was slick and I was quick, and up the stairs I sped,
    And very surprised was I to find the chandler’s wife in bed;
    And with her was a fine young man of most incredible size,
    And they were having a KNOCK KNOCK KNOCK right before my eyes.
    And they were having a KNOCK KNOCK KNOCK right before my eyes.

    When the fun was over and done and the lady raised her head,
    She was quite surprised to find me standing by the bed
    “If you would keep my secret sir, if you would be so kind,
    You may drop in for a KNOCK KNOCK KNOCK whenever you feel inclined.”
    “You may drop in for a KNOCK KNOCK KNOCK whenever you feel inclined.”

    So, many a day and many a night when the chandler wasn’t home,
    Down to the chandler shop, for candles I would roam.
    But nary a one she gave to me, but gave to me instead,
    Just a little bit more of the KNOCK KNOCK KNOCK to light my way to bed.
    Just a little bit more of the KNOCK KNOCK KNOCK to light my way to bed.

    So, all you married men take heed, whenever you go to town,
    If you must leave your woman alone, be sure to tie her down.
    Or, if you would be kind to her, just lay her right down on the floor,
    And give her so much of that KNOCK KNOCK KNOCK she doesn’t want any more.
    And give her so much of that KNOCK KNOCK KNOCK she doesn’t want any more.