Refers to material used to catch a spark and start a fire, such as charred cloth or dry plant matter. Archaic or highly specialized; modern Japanese usually uses 火口 (ほくち) or 着火剤.
melted candle wax
Specifically refers to wax that has melted and dripped from a candle. Rare and possibly obsolete; modern speakers would normally say ろうそくの溶けた蝋.
In old flint-and-steel methods, they dropped sparks onto tinder to start a fire.
In old texts, 火糞 can refer to melted candle wax.