Just had to get me to do a web search, didn't you? According to
Even after the denarius was no longer regularly issued, it continued
to be used as an accounting device and the name was applied to later
Roman coins in a way that is not understood. The lasting legacy of
the denarius can be seen in the use of "d" as the abbreviation for
the old French denier and the British penny prior to 1971. The
denarius also survives in the common Arabic name for a currency unit,
the dinar used from pre-Islamic times, and still used in several
modern Arabic-speaking nations. The Italian word denaro, Spanish word
dinero, and the Portuguese word dinheiro, all meaning money, are also
derived from Latin "denarius."
BTW, pwt is an accepted alternate abbreviation.
Also, nails (the kind you drive with a hammer) are sized by pennies
and the "d" is also used for them, eg. 10d, 12d. A long time ago,
this was the cost of buying 100 of these nails. You could buy 100 10d
nails for ten pennies, or 100 12d nails for 12 pennies. The larger
the nail, naturally, the more you had to pay for 100.
Dr. H. D. (Del) Pearson