The phrase is used several times in literature in the following years. The change from the use of ‘good’, as meaning ‘genuine’ to ‘good’, as meaning ‘well-behaved’ didn’t take long. Charles Dickens used it in the latter sense in A Christmas Carol, 1843:
“And how did little Tim behave?” asked Mrs. Cratchit…
“As good as gold,” said Bob, “and better.
The idiom as good as gold has changed a lot from its original meaning because it initially referred to something that was real and genuine. In the past, many people conducted business using credit notes, a document that promised payment within a certain amount of time. Some customers paid on time but others delayed payment or used forged or counterfeited credit notes to avoid paying altogether. Being distrustful, many business owners much preferred being paid in gold and silver, as this form of currency was real, tangible and more importantly, the payment was immediate.
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