I did know Lucille is his guitar, but no idea what B.B. stands for, without going to Google.
Steve, correct. BB named all of his guitars Lucille. The first question was more obscure. I haven't checked Google to see if it's there, but I did a lot of listening to the old AM radio clear channel stations when I was driving over the road trucks at night in the 50s and early 60s. You may have also. WLAC in Nashville, WCKY in Cincinnati, WWL in New Orleans, etc. John R was the late night disc jockey on WLAC. He played a lot of BB King, Muddy Waters, Howling Wolf, Gate Mouth Brown, etc. Early on BB was called Blues Boy King. It got shortened to BB. So, now you know. Now, I will see if Google agrees.