From the OED:
Cove, n.2
slang (orig. Thieves' cant)

(kv) Forms: 6-7 cofe, 6 coff, 7- cove. [The early variant cofe has suggested that this is identical with Sc. COFE n., 'chapman, pedlar', the sense having undergone the same transition as in CHAP, which is now nearly equivalent in meaning, save that cove belongs to a lower and more slangy stratum of speech. But the phonetic change of f to v, at so late a date, is not usual; and the origin of the word still remains obscure. Cf. also CO n.2]

A fellow, 'chap', 'customer'; sometimes = BOSS n.6 (see quots. 1812, 1891).
Frequent in the 20th century in Austral. sources.

1567 HARMAN Caveat 84 A gentry cofe, a noble or gentleman. Ibid. 86 What, stowe you, bene cofe..What, holde your peace, good fellowe.
1609 DEKKER Lanth. & Candle Lt. Wks. 1884-5 III. 196 The word Coue, or Cofe, or Cuffin, signifies a Man, a Fellow, &c...a good fellow is a Bene Cofe.
1621 B. JONSON Gipsies Metamorph. Wks. (Rtldg.) 619/2 There's a gentry cove here, Is the top of the shire. a1700 B. E. Dict. Cant. Crew, Cofe, c. as Cove.
1737 in Logan Pedlar's Pack (1869) 147 Now my Kinchin Cove is gone.
1812 J. H. VAUX Flash Dict. s.v., The master of a house or shop is called the Cove..; when joined to particular words, as a cross-cove, a flash-cove, a leary-cove, &c., it simply implies a man of those several descriptions.
1838 DICKENS O. Twist x, That old cove at the book-stall.
1891 N. GOULD Doub. Event 115, I am not in the habit of being called a cove.
1891 LENTZNER Australian Word-bk., Cove, master or overseer of an Australian station.
1911 C. E. W. BEAN 'Dreadnought' of Darling xxxiii. 288 Recollec' that cove with a red beard.
1916 Anzac Book 65 Then a corporal called and wanted to know..when would the rubber boots be ready for the coves in the trenches?
1916 J. B. COOPER Coo-oo-ee vii. 84 'He's one of those smart coves,' said Sam.
1944 F. CLUNE Red Heart 67 'Must be a balmy cove,' whispered one of the hangers-on as he tapped his forehead.
1966 'J. HACKSTON' Father clears Out 190 The young coves round about combed their hair back with soap to keep it in position.
1969 Advertiser (Adelaide) 12 May 5/4 You Aussie coves are just a bunch of drongoes.