根も葉も火種も — is it proverbial?

Question

I suspect「根も葉も火種も」 is an allusion to something I do not recognize. To what does it refer?

Consider this couplet from an amusing song released in March by IOSYS called 「ステマの女」(CD and promotional Flash animation, that can be found on YouTube or NND):

ウワサは揺らめく 霧の中
根も葉も火種も ありゃしない

根も葉もない is an idiom that means "unfounded rumor".
How did it come to have this meaning from 根 and 葉?
What does the addition of 火種 and the change from ない to ありゃしない do to the idiom?

Answer 1

About 「根も葉もない」, only 「根」 and 「ない」 are important to form the meaning, 「葉」 is added as a way of humor.

「火種」 may be referring to another idiom about rumors, 「火のないところに煙は立たぬ」 which means "if there is no fire , there is no smoke (rumor) rising." Addition of 「火種」 works as an enhancement for 「根も葉もない」. 「根も葉も火種も」 is not a common idiom. It seems the song writer mixed two idioms to form the phrase.

「ありゃしない」 is an informal form of 「ありやしない」 and it has the same meaning as 「ない」. Use of 「ありゃしない」 may imply that the singer is somehow upset about people spreading unfounded rumors.

Answer 2

No it is not a proverb, but it includes a fragment of an idiom.