'To dig' - the unusual usage
The well-known poem of Roald Dahl starts with a line "The animal I really dig among all others is the pig..."
The meaning of the verb "to dig" here is "to like" or "to adore".

My question is whether this usage of "to dig" is common or is it a sort of extravagance and an oldfashioned?

The whole version of the poem may be seen at:
https://www.youtube.com/watch?v=F5DS2DnsJ04&t=29s

Question

'To dig' - the unusual usage
The well-known poem of Roald Dahl starts with a line "The animal I really dig among all others is the pig..."
The meaning of the verb "to dig" here is "to like" or "to adore".

My question is whether this usage of "to dig" is common or is it a sort of extravagance and an oldfashioned?

The whole version of the poem may be seen at:
https://www.youtube.com/watch?v=F5DS2DnsJ04&t=29s

Answer

Yes, it used to be very common indeed in the 1960s and 1970s. If you listen to interviews from that period, you're sure to hear pop musicians and all sorts of people from the hippy era using 'dig' to mean like or appreciate.

Despite being outdated, it's still understood today. It's rarely used, though. File it away in your passive vocabulary.

Answer

"To dig something or someone" is passé and old-fashioned although some people of a certain generation may still use this construction.  It's still okay to use it but remember it's a dated expression like saying something is 'groovy'.  Check out the movie "Austin Powers" to get a feel for the time period when these words were used more frequently.

Answer

Su Ki is spot on, it was very common in the 60s/70s. But, not so much now.