Taken from the urbandictionary definition of "forrest":

"Although commonly thought to be derived from the English word 'forest' which is a "large woody area," it is actually the reverse. It was a name, 'Forrest', first with an ancient Greek translation of "Large Penis." When looking for a name for a "large woody area," the English adapted what they already knew had "large wood," to the slightly altered spelling, 'forest.' Basically, Forrest is a name for a person with a huge dick."

But infact, the above quotation is wrong. The word "forrest" was mispelled and was meant to be "forrestt". Forrestt is all of the above and more. Generally a Forrestt sucks major ass at first person shooter games such as Call of Duty: Modern Warfare 2, with the exception of the Halo series, in which they generally kick ass.