Inundated means "overwhelmed" and come from several Latin root words: Unda (wave), in (into, upon) undare (to flow) and inundare, literally "to flood or to overflow."  It came into the English language in the late 16th century.  Overflowing is still one of the meanings of the adjective inundated. 

The word "inundate" was first used in English in the early 1600s. The earliest known use of the word is in 1623, in the writings of lexicographer Henry Cockeram.  The adjective inundated was first used in English in the 1870s. The earliest known use of the word was in 1875, in a text by geologist Charles Lyell. 

Just the facts:

Inundate Definition & Meaning - Merriam-Webster