Here are some well-regarded options:
* Online Etymology Dictionary: This website is a great free resource for tracing the origins of words, and it's often updated with new information.
* Oxford English Dictionary: The OED is considered the definitive dictionary of the English language, and it includes extensive historical information on words, including their origins.
* Merriam-Webster Unabridged Dictionary: Another comprehensive dictionary that provides etymological information for words.
* American Heritage Dictionary: A well-respected dictionary that also includes etymological information.
These resources will give you information on the origins of the word "dandelion," including its etymology, its history, and its various meanings across time.