Erik Frank Russell, 'And Then There Were None' (1953). Some snippets:
“‘Obligation. Why use a long word when a short one is plenty good enough? An obligation is an ob. I shift it this way: Seth Warburton, next door but one, has got half a dozen of my obs saddled on him. So I get rid of mine to you and relieve him of one of his to me by sending you around for a meal.’ He scribbled briefly on a slip of paper. ‘Give him this.’”
[…]
“‘No.’ Firmly she pushed the pineapple back at him. ‘If I ate my way through that I’d be saddled with an ob.’
‘So what?’
‘I don’t let strangers dump obs on me.’”
(JLW)