aha is a noun meaning "rage" in Quenya.
Aha is also the name of the eleventh letter of the Tengwar alphabet.
The original name of Aha was Charma and in Quenya it had the value "ch". Over time the "ch" in Quenya softened to "h" at the beginning of words and the letter, now called Acha, was only used when the "ch" sound was explicit (eg. in the middle of words). Still later the "ch" sound disappeared altogether and the letter name as well became Aha.