I'd never heard it before, from googling it seems to be antiquated language in Britain.

I (British) am familiar with the term, especially as a verb like "fencing stolen goods". You can find British newspapers reporting this in the last decade.

The legal term since 1968 seems to be "Handling Stolen Goods", which might have made the word "fencing" less common: https://mcgeemcgeeagarlaw.co.uk/criminal-defence/handling-st...

You've gotta watch more Guy Ritchie movies.

Must have never played an elder scrolls game huh