Borussia Dortmund's first crest was a simple design that has formed the basis for all of their proceeding crests. The two striking colours, black on a yellow background, were taken from their kit colours. "BVB" are the initials for Ballspiel Verein Borussia, which roughly translates as "Ball Game Club". The 09 refers to the year that Borussia Dortmund was created, 1909. And the word "Dortmund" speaks for itself.
Dortmund decided to invert the colours on their crest in 1964, with black being made the background colour and yellow lettering on top. And just in case anyone was in any doubt as to who BVB referred to, they went the whole hog and had Borussia Dortmund displayed in full around the edge of the crest.
Ten years later and Dortmund dropped the full name and went for a simpler design, displaying only BVB 09 in the centre of the crest but with a large black ring near the outer circle.
1973 had seen another German club, Eintracht Braunschweig, cleverly managing to get around the DFB's kit sponsor ban by changing their crest to incorporate a sponsor's logo, in their case Jägermeister. So, in 1976, Borussia Dortmund followed suit when it struck a deal with Dutch tobacco brand Samson. That meant Samson's logo, a lion, then found itself smack bang in the middle of Borussia Dortmund's crest for a couple of seasons.
After the sponsorship deal finished the club reverted back to exactly the same crest that had been used before.
1993 saw the club revert back to a very similar design to their first crest. The "Dortmund" text was dropped, and the "BVB" was slightly bolder, but in essence it was almost the same. It seemed to mark a change in fortune on the pitch too - the club entering a golden period in the mid 1990s that saw it win back-to-back Bundesliga titles and then became Champions League winners. The crest hasn't been changed since.