A nickname given (by his very grateful female partner :)) to any man with a very long and thick penis (from the general perception that black men in general are more "well endowed" than their counterparts from other races).
The name "Leroy" being more common a name amongst African-American males than of any other race.
Emma: "(*sigh!*) OMG! I sorta always had the feeling
that you've got a big dick, but I never dreamed..... OMG!!!
Think we're gonna have to start calling you Leroy from now on mister!" (*sigh!!*)