Definition - A word that serves no grammatical function, but that is used either to fill out a sentence or to give emphasis.

Example -
I just got access to Google. Yahoo!

Etymology -
The term originally denoted "a word or phrase serving to fill out a sentence or metrical line." That sense derived from the Late Latin expletivus, serving to fill out (from ex-, out + plere, to fill). Its use in the sense of "exclamation" was first recorded 1815.

Oxford English Dictionary -
Its first citation is from 1677:
"He useth them [oaths] as expletive phrases … to plump his speech."
(Barrow Wks. (1741) I. xv. 10)

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