Did Australia use to be part of new holland?

Yes, Australia used to be part of the continent called New Holland.

The name "New Holland" was first given to Australia by Dutch explorer Abel Tasman in 1644. The name was later used by other European explorers, including James Cook, who used it in his 1770 map of Australia.

The name "New Holland" was eventually dropped in favor of the name "Australia" in the early 19th century. The first official use of the name "Australia" was in 1817, when it was used by the British Admiralty.

The name "Australia" is derived from the Latin word "australis", meaning "southern". The name is appropriate for Australia, as it is the most southerly continent on Earth.