On Wed, Jul 06, 2016 at 03:22:35PM -0700, C. Berry wrote:
> Similarly, the gram is a convenient mass unit for some scientists,
> but the kilogram is more convenient for most real-world uses, so the
> latter gets treated as the base mass unit for a lot of purposes.

The kilogram has been a base unit for the whole history of the metric
system, though originally called the grave with unit symbol G.  A
prototype mass standard was manufactured to its specification.  The
original name for 1/1000th of a grave was a gravet, but a few years
later the names "grave" and "gravet" were considered too aristocratic
and dropped for political reasons in favour of a new name "gramme" and
its power-of-ten prefixes.  The fundamental mass standard remained the
same, however.  New mass standards were manufactured in 1799 and 1889,
but were still based on the original grave (kilogram) unit.

The unit "are" also dates back to the 18th century and the original
French Revolutionary units.  When it was originally developed, prefix
naming from a base unit hadn't been fully established and units had
individual names for some of their decimal multiples.  Among these was
"are" as a synonym for a square decametre.  It survived while the
others did not, much as the litre did for volume.

- Tim