Green’s Dictionary of Slang

1. a generic term for a man, on lines of such equally common names as Jack, Tom etc.

1905		‘It’s Only a Way He’s Got’ in ‘Banjo’ Paterson Old Bush Songs 85: Says she, ‘Oh, take no notice, Bob, / It’s only a way he’s got.’.
1937–84		Partridge DSUE (1984) 106/2: from ca. 1700.
1977		D. Powis Signs of Crime 174: Bob Friend or ‘mate’ (hippy term).

2. see Bob Hope n. (1)