make a hash of

make a hash of (something)

To ruin, bungle, or spoil something. I really made a hash of that project at work—I'm going to get fired for sure! I'm afraid the accounting department made a complete hash of these numbers. We'll need to re-tally the entire ledger.
See also: hash, make, of

make a hash of

Also, make a mess of. Ruin or spoil something, as in They've made a hash of their financial affairs, or She thought he'd make a mess of the garden. The first term, first recorded in 1833, uses hash in the sense of "a jumble of mangled fragments"; the variant, using mess in the sense of "a muddle" or "a state of confusion," was first recorded in 1862.
See also: hash, make, of

make a hash of

make a mess of; bungle. informal
Hash comes from the French verb hacher meaning ‘chop up small’. A hash is a dish of cooked meat cut into small pieces and recooked with gravy; from this comes the derogatory sense of hash meaning ‘a jumble of incongruous elements; a mess’.
See also: hash, make, of

make a ˈmess/ˈhash of something/of doing something

(informal) do something very badly: We tried making some wine, but we made a mess of it (= it did not taste good).I made a complete hash of the whole exam.
See also: hash, make, mess, of, something
References in classic literature ?
Is to do what you most want, to live under the conditions that please you, in peace with yourself, to make a hash of life; and is it success to be an eminent surgeon with ten thousand a year and a beautiful wife?