[none_to_remain]

Of course! I was being silly and just thinking of "k" for the smaller one and "K" for the bigger one.

[EuanReid]

Upper-K is for Kelvin, so can't be mixed in as a prefix in case someone decides to commit physics crimes and talk about temperature-mass (Kkg).

[nayuki]

Not true. Several SI prefixes already overlap with units. m is both metre and milli-. T is tesla and tera-. c is a prefix of candela (cd) but also centi-. (G is gauss (cgs unit, not mks/SI) and giga-.)

[adiabatichottub]

Just throw some Joules on top there and it'll be alright