A Russian traveller named Putimtsoff was the first to visit the lake in 1811. He gave a good description of it, mentioning about rocks of different colours in the lake, and the furious winds blowing around the lake. Thirty years later Alexander Schrenk explored the lake and its surroundings.
Literally, the name Ala-kul would mean 'variegated lake,' although it probably takes its name from the Ala-Таu mountains lying further north.
Thank you Roman!