Its etymology is uncertain. It may derive from "newie", which is attested in U.S. and Australian sources of the 1850s and means a neophyte in a place or situation; alternatively, it may derive from the British public school slang "new boy", which is attributed to the same era and was applied to a schoolboy in his first term.
In the 1960sâ€“1970s the term "newbie" had a limited usage among U.S. troops in the Vietnam War as a slang term for a new man in a unit. Its earliest known usage on the Internet may have been on the Usenet newsgroup talk.bizarre. The term is believed to have entered online usage by 1981
Suddenly, I feel old. I was a newbie in online games in 1994. Shorthands and misspellings have bled their way into common usage for years. I do know that the term has been used online since at least the mid '80s... but it has trace roots that date back to the '60s describing new recruits in Vietnam as a variant of "new boy" ... etc, etc.