The word was "Brobdingnagian", which apparently means "giant", from the book, Brobdingnag, published in the 1700s. I know all of the words you listed, even if I don't know t he books they came from, on the other hand, I've never heard anyone use "Brobdingnagian" and I've never heard of the book it came from either.
Strangely, I knew this one. Once you hear this word it refuses to leave your head.
I don't know that one, but I do know gargantuan, and pantagruelian, which come from a 17th century novel by Rabelais as well as yahoo and Lilliputian, which come from a 1726 novel by Swift.
gargantuan and yahoo are common parlance, people actually use these, in spite of them not knowing their origin. When's the last time you've seen those written down, or spoken, anywhere aside from those nearly half millennia old books? I've never seen those.
"Yahoo" and "Lilliputian" come from the same 1726 novel by Swift as "Brobdingnagian".