I was in highschool in the 1980s and I played a lot of Warhammer 40K (I played Orks and the Shokk Attack gun was way cooler back then, trust me) and listened to/watched a lot of Monty Python. Yep... the ladies were all over me. There was a Monty Python skit called "String" in which Eric Idle (and yes, I know I said it was Michael Palin in episode zero) goes into an advertising agency and meets with an ad exec named Adrian Wapcaplet played by John Cleese. So that's where the word came from. I told you that story so I could tell you this one. The space marines in those days came on plastic sprues and had beaks. They also had these bumpy shoulder pads and my friends and I referred to those shoulder pads as wapcaplets because we were freakin' hilarious and that was the only thing that it made sense to call them. So, since "wapcaplets " were small and had to do with gaming I named this show after them.
That explanation was probably way longer than you wanted it to be and way less funny than you hoped it would be but it's true.