First, desired profit is the markup rate. Note, since you are using 100 in this formula the market rate must be input as a percentage, not decimal. "100 - markup rate" does not have a name. I suppose you could call it the markup rate complement. Technically, that's what is its. Complementary percentages simply add up to 100%.
It might be helpful to see where the formula comes from. What you are looking for is a selling price that equals cost plus a percentage (the markup rate) of the selling price. Or:
$S = C + SM$
$S - SM = C$ (Solving for S)
$S(1-M) = C$
$S = \frac{C}{1-M}$
This is the same formula, but enter the markup rate as a decimal and you do not have to multiply by 100.