The word "this" is a demonstrative pronoun that refers to a specific thing or person that is close in distance or time to the speaker. It is often used to indicate or emphasize a particular item, idea, or individual that has just been mentioned or is present in the current context.
The word "this" originates from Old English "þis" (also spelled "þes"), which is related to the Proto-Germanic "þiz," and ultimately ties back to the Proto-Indo-European root "tis," indicating something close to the speaker.