So let's get gather some opinions on the spelling here.
1. The item in Minecraft is with one 'l' - Lily Pad
2. From what I can find, Lily is the spelling of the flower, while Lilly is a female name.
It seems Beef is changing between the spellings. Note Episode 20 as Lilly then Episode 21 as Lily then Episode 114 as Lilly again.
- I'd opt for "lily pad". As I understand and as you found, it is the correct spelling of the term, both in Minecraft and in English (at least the American kind :) ). Beef has no real reason to refer to it as a person (also from what I can tell), so any subsequent spellings as "lilly" are probably spelling errors. Also, I believe this is when he first plans out the build. He refers to it as "lily" in this episode. --Aejrogota (talk) 18:13, 19 May 2014 (CEST)