Apparently it was a nickname given to a WWII tank commander by his crew...
The Real War Daddy – Destroyed 12 Tanks and 258 Armoured Vehicles in 81 Days
World War II saw the emergence of tank Aces who became famous for their incredible milestones at the war front. Among the most widely recognized tank crew and tank platoon commander was the American Ace of Aces, Lafayette G. Pool. Pool killed over 1000 German soldiers and took 250 as war prisoners. Furthermore, he destroyed 12 tanks, 258 armored vehicles, and self-propelled guns. He achieved all these within a period of 81 days, using three different Sherman Tanks from 27th June to 15th September, 1944.
Pool’s successful encounters in the war led him to be nicknamed “War Daddy” by his crew. A movie, ‘Fury’, made to his honor was released in 2014 and was played by Brad Pitt.
So, yeah, I'm hoping you guys don't find a War Daddy for your DLine, too lol...