Yeti, also known as the Abominable Shitman was part of a legend which thrived on several planets in the Galaxy, as well as the non-existent planet Earth.
OK, let's see how the legend made to a place which doesn't exist in the first place.
Legend goes that famed explorer Lando Calrissian was hiking around the ice world of Hoth when suddenly he came across a gigantic footprint in the SNOW. Likewise, Hoth had no mythology nor legends of its own so Calrissian immediately said it was some yet unknown animal which nobody had yet seen.
Since then, rumours of the creature spread, with many people seeing gigantic, humanoid ape-like critters in the SNOW, and many of them hearing unusual noises in the mounts of Hoth. Many people tried to debunk the rumours, saying that the name Yeti was actually a corrupted form of the Sand People's bear but this was immediately accused of being racist, man, and nobody would want that, eh?
Some people said that the so-called Yeti was actually a Stormtrooper who had got tired of the long life on the front lines and flew his ship to Hoth to live a quiet life of retirement... Special favour from Dumbledore, see, one year, and then back to quiet retirement. Anyhow, the Yeti gained fame despite the constant criticism. Many suggested bears were the culprit, although as far as we know bears only exist on the non-existent planet of Earth and therefore are themselves non-existent, and many suggested that in fact, Ewoks were to blame for sightings.
In 2007 of Hoth time, a hiker was said to have seen a large, hairy, ape-like creature, trying to hunt him down and cook him as stew. His Sand People guides debunked this.
In 2008, an explorer was said to have photographed a Yeti at close quarters and was determined not to rest 'til he had the thing's head on a plate.
In 2009, an explorer was banned from Hoth and put on the Death Star, working on the canteen, when he was charged with illegally smuggling Yeti scalps to Coruscant.
In 2010, a Yeti was photographed. It turned out to be an Ewok in disguise.
The following statement has been concluded by Darth Obvious and is not considered canon.
It is obvious, really, that the Yeti is a Wookie.