Correct spelling, explanation: holiday is derived from two words holy and day where y was replaced by i. The word is originated in Old English, referring to a religious anniversary. There is no need to add the second consonant l because in the word holy we have one l. Besides, there is no rule saying to do that. To sum up, considering the origin of the word, exclusively holiday is the appropriate form of a noun but holliday is spelled incorrectly.

Definition of holiday:
noun/verb, a period of time where you relax without work or school in traveling or simply you do what you want because it is your free time.
Last year they were on a skiing holiday in winter but I prefer a camping holiday in summer.
Betty loves foreign holidays but she can’t really afford them.

Phrases with holiday:
bank holiday – time when many businesses, for example, shops, banks, and schools are closed for the day,
Remember that all stores will be closed for the bank holiday on Thursday.
package holiday – a period of your free time organized by a travel company,
She booked a package holiday for her parents in France.

Incorrect spelling, explanation: holliday is an improper form of a noun that consists of two parts of speech: the adjective holy and the noun day. It has its roots in Old English, which means that it is one of the oldest words in this language. The form holliday has never been used in English. In Middle English, it was known as haliday with one l and nowadays we have the form holiday which is the solely correct word in this case. However, holliday can be a typo or a misspelling and the learners of English should check the proper spelling of the word and use it correctly as holiday, not holliday.

Incorrect spelling

Incorrect spelling