Up to five extra ranks (+5) can be obtained from the skill bonuses of Legendary Mechromancer and Legendary Roboteer class mods.
Legendary Mechromancer class mods also provide their own additional bonus to action skill cooldown rate. All cooldown modifiers are summed together as bonuses in the function T = baseTime / (1 + bonuses), regardless of their source (e.g. skill, relic, mod, and a friendly Siren wearing a Binder class mod).
The skill's name is a reference to My Little Pony: Friendship is Magic, where one of the main characters, Rainbow Dash, arbitrarily notes that "[her dress] needs to be about 20% cooler." This has since become a meme among fans.