Green’s Dictionary of Slang

to a great extent, unreservedly, ostentatiously.

1853		N.Y. Clipper 31 Dec. 3/4: This is piling it on rather extensive, but New Year’s Day comes but once a year.
1877		‘’Arry on His ’Oliday’ in Punch 13 Oct. 161/1: Jest wouldn’t we go it extensive!