Green’s Dictionary of Slang

an exhortation to relax, e.g. don’t get flustered! stay calm!

1754		Trial of Elizabeth Canning in Howell State Trials (1816) 412: Upon my word, I can't tell; there were words passed, but I don't believe there were many; when he hulled the dust in, they bid him be easy.
1793		W. Macready Irishman in London II ii: Arrah! is it my own daffy-down-dilly you want, Maister Pat, to bring home? Oh thunder! Arrah be asy!
1797		M. Robinson Walsingham III (1805) 33: ‘Ah now! be azey!’ cried Mrs. O’Liffy.
1806		G. Colman Yngr John Bull II ii: Oh, be asy!
c.1813		‘This London Agrah!’ in Wellington’s Laurels 8: Sing diddaroo daisy, my jewel, be aisy.
1818		‘A. Burton’ Adventures of Johnny Newcome IV 204: easy, champ!, Be asy—don’t be after joking.
1825		Egan Life of an Actor 45: ‘Oh, be aisy, man,’ interrupted the incredulous ostler.
1832		S. Warren Diary of a Late Physician in Works (1854) III 136: Och, aisy, aisy wid ye!
1837		Marryat Snarleyyow I 246: ‘Be aisy, my jewel,’ replied Nancy, mimicking the Irishman.
1842		S. Lover Handy Andy 30: Oh, be aisy, Tom.
1848		D.O. Madden Revelations of Ireland 115: ‘Easy now,’ cried O’Connell.
1879		G.G. Hart E.C.B. Susan Jane 19: Oh I say, Cap., be easy old man.
1897		Boy’s Own Paper 6 Nov. 83: ‘Easy all,’ the Lieutenant ordered.
1900		Boy’s Own Paper 22 Dec. 178: He at once laid hold of Jake, saying in his cool determined way: ‘Easy now, stranger, easy’s the word’.
1902		Bulletin Reciter 1880–1901 84: Now, be aisy! / But poor Casey’s gone on tramp.
1910		‘O. Henry’ ‘Past One at Rooney’s’ in Strictly Business (1915) 257: Wow – ouch! Easy, boys!
1919		Marvel 1 Mar. 8: Easy all, you frumps!
1925		Black Mask Aug. III 56: ‘Easy, Al’ Adams warned.
1934		H. Roth Call It Sleep (1977) 267: Easy Kushy! [...] Easy! Easy!
1939		Rover 18 Feb. 16: Easy, boys, easy.
1942		(con. 1890s) S. O’Casey Pictures in the Hallway 75: Easy, easy, murmured the other constable.
1951		A. Garve Murder in Moscow (1994) 68: ‘Easy, Jeff!’ I protested.
1954		(con. 1940s) T.A.G. Hungerford Sowers of the Wind 152: ‘Easy, greasy,’ McNaughton said [...] ‘If the lady says she wants to dance with me, then it’s up to her.’.
1959		A. Zugsmith Beat Generation 31: ‘Easy, easy!‘ called one of the human building bocks.
1962		A. Wesker Chips with Everything I xi: pip: Each time you say ‘always’ the world takes two steps backward and stops bothering. And so it should, my God, so it should – wilfe: Easy, airman, easy.
1976		P. Theroux Family Arsenal 142: Easy, squire.
1981		A. Payne ‘You Need Hands’ Minder [TV script] 27: Easy, Des, easy. I had no idea it was that serious.
1989		P. Munro Sl. U. 75: Easy!/Easy, tiger!/Easy, sober!/Easy champ! Calm down!
1993		Cody High School Times in Detroit Free Press (MI) 11 May 49/6: Class of 1993 gives Shout Out. I would like to send shout-outs to [...] Alexis and sexy tyrone and the whole class of ’93. Be easy!
1996		J. Cameron It Was An Accident 133: He drove that motor like he hated it. ‘Easy John,’ I goes.
2000		T. Udo Vatican Bloodbath 35: ‘Easy,’ said Shaftesbury. ‘We’re all on the same side here.’.
2002		L. Rutman Thy Father’s Son 230: ‘Easy champ.’ He is incredibly strong. His hand encircles my wrist. ‘Turn it off, sonny.’.
2005		B. Hare Urban Grimshaw 87: Easy, charver. I’m Pinky.
2007		J. Butcher White Night 283: I put a hand on Ramirez’s wrist and said, ‘Easy, tiger. It’s a friendly.’.