Can I come and see you at oncer Poirot let a few moments elapse before he answered.

In Britain tenner, tanner, bob, oncer, guinea, quid, and other terms were in common use in conversation when purchasing an item.

In the 1980s, as the pound coin was replacing the pound note, Watts bought several hundreds of the latter from a bank so that the Crisp Oncer prize could continue.

This concluded with the Great Corny Joke Contest, offering a cash prize of a "Crisp Oncer" - at £1 "the meanest prize in Fleet Street", and one which became relatively meaner as the years passed.

Fiver and tenner (for five and ten pound note respectively) probably do fit the "-er" mould, as, more obviously, does oncer (one pound note), though this was always less prevalent than the higher denominations and is virtually obsolete following the introduction of the pound coin in 1983.