Khlong Dusit derived its name from the monastery Wat Dusit situated on its east bank. Dusit is the Thai translation for the Sanskrit word "Tush" meaning "to be content" or "that in which all desires are satisfied". It is referring to the "Tushita Heaven", the "joyful heaven" or "the heavens of the joyous", the fourth Deva heaven above the earth in which the almost perfect beings, about to become Buddhas, pass their last angelic life before being born on earth to assume the Buddha hood. [2]
The long gone Wat Jula Mani and Wat Chaofa Rasami stood respectively at its mouth respectively on the east and west bank of the canal, at the confluence with Khlong Ban Bat and Khlong Kramang. Wat Sam Plum, of which chedi is a landmark of Ayutthaya, stood on its east bank, north of Wat Dusit.
Khlong Dusit connected Khlong Ban Bat and Khlong Kramang with Khlong Khao San. It was an important canal as it gave access to one of the most important temples of the Ayutthayan era: Wat Yai Chai Mongkhon. References:
[1] Our Wars with The Burmese - Prince Damrong Rajanubhab (1917) - Re-edited White lotus (2000). [2] The Wheel of the Law - Alabaster Henry (1871) - Page 177.