Three things could happen.
3 letter names osrs. The steps to getting your own 3 or 4 maybe even 2 letternumber username are very simple. Depends how you define rare. Letter to surok a quest item obtained during What Lies Below.
You can easily buy one from 3rd party sites for a few mil. Ilujanka names - RuneScape. You will also have to pay for all transferMM fees.
The lowest I will go is 50k per name. Guide on how to make a 3 letter name on Runescape. To obtain one via in game change Id imagine there is none left and only obtainable when names are released.
Given that there was a name release 2 years ago thousands of these names are likely still available. Sythe is the largest and most trusted marketplace for runescape names. Not all of these are available.
3 Letter names and Unique Names If you want to request a specific name Ill do my best to get you it. Still considered a rare name. Firstly add any names you are interested in into your Ignore tab.
Ive seen a couple 1 letter names although not all in OSRS. The Ilujanka also known as Lizardmen are a race of reptilian humanoids from the realm of Iaia. If its just 3 random letters then probably nothing as theres plenty of them around and available.