Here is where you have made a subtle exegetical blunder with the language.
If you look at every occurance in the NT of this word and its various forms, you would have seen that this word ONLY occurs in the passive voice in the NT. Therefore, you should be looking at the sections in the lexicon that show the definition when the passive voice is used. With this critical information, the lexicon would offer its meaning as "to suffer loss, to forfeit something."
Baur, Gingrich, et. al. have clearly documented usage of this word outside the NT; the sub-title of their combined lexicon affirms this. But the NT usage is restricted to the passive voice.
For example, Matt. 16:26, "what does it profit a man if he gains the whole world but ζημιωθη his soul?"
The context clearly indicates the loss of something previously possessed, not the punishment of the soul ... but its complete loss. All the other occurances are the same, passive voice, meaning is clearly "loose something that you could have had, or loose something that you previously had."
Similarly with Mark 8:36, Luke 9:25, 2 Cor. 7:9, and Phil. 3:8. All passive voice, like 1 Cor. 3:15, all meaning "to loose something."
Are you asserting that my seven corroborating sources are ridiculous?
No, I'm asserting that with proper care, these resources can guide you to the correct exegetical understanding of the passage in question ... which, unfortunately, has eluded you to date.
I made no blunder because I do not rely upon forensic exegesis to reshape what Tradition already confirms.
The concept of purgation was widely known throughout the first century Mediterranean. The process of purgation was used in food preparation (i.e.; snails were purged before cooking) Medicine ( i.e.; blood letting induced vomiting, sweating, etc.), population control and even criminal and punishment. It was seen as both cleansing and redemptive. The transition of the soul of a sinner from a condition of sin to a fully cleansed state suitable for entry into heaven was considered a purgation. Purgatory was merely that state of being where/when purgation occurred. The Church never described it as a place.
By the way, it really is silly for Protestants to take a lawyerly approach to the development of the language used to refer to the new ideas of Revelation and try to link the inception of the idea to the branding of it.
Peace be with you.