What was 'Van Dieman's Land' is now called 'Tasmania'. Why?

It used to be called Van Diemen's Land after a Dutch governor named Anthony van Diemen, because the Dutch explorer Abel Tasman named it that in 1642 to honour his boss.

But later, when the British took over, the name got a bad reputation because the island became known for its harsh convict prisons. So in 1856, they decided to change the name to Tasmania, after Abel Tasman himself, the guy who first spotted it, to give the place a fresh start and a better image.

Basically: same island, new name, less baggage.

Link for above:

The name "Van Diemen's Land" was changed to "Tasmania" in 1856. The change was initiated by the British colonial authorities and ultimately approved by Queen Victoria. The name change was brought about through an act of the British Parliament known as the "Van Diemen's Land Name Act 1856." The act received royal assent on 1st January 1856, and that's when the name officially changed. However, the usage of the new name took some time to become widespread. The initiative for the name change came from the colonial authorities in Van Diemen's Land. The decision was likely influenced by various political, social, and economic factors of the time.

The name change was primarily motivated by a desire to disassociate the island from the stigma of its convict past. Van Diemen's Land had been established as a British penal colony in 1803, and its name had become synonymous with convict transportation and harsh penal conditions. By renaming the island to Tasmania, the authorities aimed to create a fresh identity for the colony.

https://dutchaustralianculturalcentre.com.au/archive/dutch-australian-history/van-diemens-land-became-tasmania-1642-1856/