They can both be adjectives, but with different meanings ("a nothingblank job" / "a blanknothing piece of paper").
Other than that, blank is a noun or a verb, and nothing is a pronoun or adverb.
I did get it though, because they are very similar.
G'head Guizz Master, delete away
Ah... come to think of it, after reading the comments. Maybe most didnt read instructions? About it being a chain. Not that for many I needed the letters. But still. (tokyo, tango (several 5 letter ones), blank, kanji, and yemen (as others have stated, not the only 5 letter option). But well then after some tries I still would ve gotten tango and yemen. (and good chance for tokyo)
After checking : okay, I had no idea there were bones named that way. Pretty weird.
humorous - funny