Basically the stuff that fat turns into when bodies decompose. If you’re up to it an image search is pretty informative but it’s not a picture I’d want to post here.
腐敗を免れ蝋 - the wax that escapes from decomposing
蝋化した死体 - (changed to) waxy corpse (roughly)
When writing the above, my IME wouldn’t get the kanji for ろう unless I used 死蝋 and deleted the 死, so while ろう would be something the reader would know, 死蝋, like the English grave wax, would probably need a note to explain what it is.
Random Japanese connection: the book Urn Burial is mentioned in Natsume Soseki’s novel Sanshiro. The protagonist (a Japanese university student reading it in English) finds it an extremely difficult read
But now I’m wondering if it was the prose or whether a Japanese University Student of that era would have been familiar with Greek/Latin mythology since Pompey and Theseus get name dropped in the first 3 paragraphs.
Soseki taught English Literature at Tokyo Imperial University in that period, so he is “writing what he knows” both in Sanshiro and Wagahai wa Neko de Aru (which has various characters who’ve graduated from university). Both are stuffed full of offhand references to the Western literary canon including the usual Greek and Roman suspects. I don’t suppose Soseki was exactly a typical student, but I reckon a fair amount of this would have been on the Eng Lit undergrad curriculum. (Soseki is also assuming his own readers are able to take passing references to Plato in their stride, for that matter. My modern editions come with a big endnotes section to assist the less educated reader…)
Yeah 別に is like a qualifier or an intensifier and it’s usually associated with being kind of a double negative since it changes from “especially” to “not especially” in a negative sentence so I can see why.