(Shuukou kin wo tokasu;
“The mouths of the masses melt metal.”)
Rumor and slander tend to get worse as they spread. The power of many people all talking about something is to be feared, because even correct information has a tendency to get altered or distorted. The phrase invokes the terrifying power of a smelter, which can reduce even strong metals to liquid.
We begin with compound noun 衆口 (shuukou), literally “the mouth of the masses,” i.e. something that many people are talking about. A possible clarifying particle is elided, and we move straight to a verb phrase. This is the verb 鑠く (toku), “to melt,” with the particle を (wo) marking the noun 金 (kin), “gold,” or by extension “metal,” as its direct object. The verb appears in imperfective form, with causative suffix す (su), in sentence-final form.
This saying comes to us from the Discourses of the States (國語, in current Japanese 国語, Kokugo), a 4th century BCE compilation of speeches (“discourses”) attributed to various famous historical figures.
The character 鑠 is no longer in common usage and may be hard to produce by typing. It looks like it can be replaced by near-synonymous homophone 爍 (near-synonymous because 鑠 carries a secondary meaning of “charmed, captivated,” while 爍 carries a secondary meaning of “to shine”). None of my sources use 鎔 or 熔, the moderns character for “melt [metal].”
(Kaji-kun wa koushoku ni tsuite kara sugu ni uwasa no osoroshisa wo shiri, shuukou ni wa kin wo tokasu hodo no chikara ga aru to satorimashita.)
[After taking public office, Kaji quickly became acquainted with how frightening rumor is, and came to realize that public discussion can have the power of a blast furnace.]