As the name Venus is a roman goddess I assume it must be the Romans that first knew it as Venus, but I am sure it was known as something else before that.

I think the Greeks saw her coming up on a clam shell.

The Romans called the Planet Venus "Lucifer" They didnt call it a Planet, they called it a Star, Venus can only be seen in the morning as the brightest star before sunrise, Thus they called it the "Morning Star" Being the brightest star before sunrise, it was thought that Lucifer summons the Sun, thus why it was called Lucifer "I Bear Light" Litterly "I bear the Light of the Morning Sun" Bible refrences Venus. 2 Peter 1:19: “We have also a more sure word of prophecy; whereunto ye do well that ye take heed, as unto a light that shineth in a dark place, until the day dawn, and the "day star" arise in your hearts:” Revelation 22:16: “I Jesus have sent mine angel to testify unto you these things in the churches. I am the root and the offspring of David, and the bright and "morning star".” Isaiah 14:12-15: “How art thou fallen from heaven, O Lucifer, son of the morning! Now in Isaiah, mentions Venus falling from the Heaven/sky, Venus Does this but in an illusion sense and nasa can prooves it. "Nasa finds Venus close to the western horizon and drifting south (left) with the passing days. By December however, Venus was climbing well above the horizon after sunset and in January 2001 it reached its maximum apparent distance (elongation) from the Sun. March found "Venus falling" from the evening sky while moving rapidly north, finally appearing (far right) as a faint dot against the sunset glow on March 24. This month, Venus rises before dawn as the brilliant morning star. " http://apod.nasa.gov/apod/ap010601.html

Probably the "cavemen"... http://www.answerbag.com/a_view/4228583