A is for Apollo. For a god. He wasn't very smart.
B is for Beta Quadrant. Most of the Klingon and Romulan Empires were located within its boundaries.
C is for Chekov. He screams a lot.
D is for Delta Vega. Galactic edge or near Vulcan. Take your pick.
E is for Epsilon Indi.
F is for French starship captains.