Green’s Dictionary of Slang

very, extremely; often as thumping great.

1781		‘Hobbies of the Times’ in Bullfinch 214: A full high crown’d hat / [...] / Like a thumping large church bucket.
1841		‘He Was Such A Queer Old Man’ Dublin Comic Songster 203: But yet a charm she could disclose, / In a thumping well fill’d purse!
c.1850		Peeping Tom (London) 29 115/2: What paddy would call thumping big potatoes.
1858		Bell’s Life in Sydney 19 June 3/2: A thumping big compatriot from the isle of bogs.
1861		(con. 1840s–50s) H. Mayhew London Labour and London Poor I 124/2: I once sold a thumping old jack-hare to a draper for 6s.
1894		Truth (Sydney) 15 Apr. 4/8: Suppose we get a thumping fine £50,000 court-house [...] erected here.
1900		Marvel XIV:344 June 5: A very, very good fifty – a thumpin’ good fifty, if you ask me.
1914		C. Holme Lonely Plough (1931) 119: Gave a thumping big subscription.
1922		Joyce Ulysses 498: After my thumping good breakfast of Metterson’s fat ham rashers and a bottle of Guinness’s porter.
1930		M. Fiaschetti You Gotta Be Rough 4: It was thumping good story-telling.
1960		H.S. Thompson letter 7 Apr. in Proud Highway (1997) 211: Get so thumping, jabbering drunk that no one will recognize me.
1999		Guardian Travel 9 Oct. 4: A medieval Moorish castle that stands on a thumping great rock.