Green’s Dictionary of Slang

1. early.

1983		(con. 1940s) D. Nobbs Second From Last in the Sack Race 40: They said they’d be here early doors.
1998		I. Welsh Filth 286: He’s round for me early doors.
2001		K. Sampson Outlaws (ms.) 23: Nirvana opens at four of a weekday, and early doors is a good time to go down there.
2018		J.-P. Jordan Joys of War 26: I had an early night and made sure I was going to be sorted early doors tomorrow .

2. early on, prematurely, as n., something that happens prematurely.

1978		D. Winter Death’s Men (1979) 228: But on the whole men withstood the pressure of early doors.
1997		‘Q’ Deadmeat 128: Early doors, he’d shown Bones a lot of the pitfalls that were lying in wait.
1999		Guardian Rev. 23 July 6: No footballer has ever uttered [...] ‘Early doors’ or ‘He’s turboed up there’.