What's That Stuff?

The biggest challenge in the remod has been the kitchen floor...testing my patience I tell ya.
100+ years of flooring, one stacked on top of the other. I've had several people tell me it would be best if I just covered up the mess by adding another layer.
Uh uh.
The top layer was curling linoleum, and there were soft spots where the dishwasher and sink each had their little hissy fits over the years. There was no way I was going to stack my new cabinets over potential dry rot?
Dumb...approaching stupid.
So, we got busy. We're down to the original t&g fir flooring, lots of water damage but no rot. The base layer of linoleum was backed with tar paper that was stuck to the floor with some kind of adhesive - I was able to get that off with my favorite Jasco stripper. But the Jasco doesn't touch some kinda wierd gunk that was under the tar streaks..it looks like floor wax, or glue of some kind.
After a lot of internet research I thought a steaming process would take it off.
Nope.
Mineral Spirits?
Nope.
Paint thinner?
Nope.
Acetone?
Nope.
I talked to another know-it-all guy at another paint store and he asked me if I'd tried Denatured Alcohol...he was sure that would take it right off - so I bought it.
Nope.
Then I remembered that a friend had told me her husband had the same problem with the floor in their bungalow. He'd tried absolutely everything and then someone told him to use boiling water. I tried it...scrubbing with steel wool right after pouring on the water - - - it worked! The boiling water/steel wool scrub turns that gunk to muddy water. It's a really slow process and the water has to be boiling or it's a no-go.
I talked to that friend this week and asked her who told her hubby about the boiling water trick...he told her it was me.
Yikes.
I hate middle-age brain fog...I seem to have lost a few chunks of really good data.
If you find my data would you please be so kind as to send it to me?
Oh ya...and if you have a really old house with strange gunk on the original wood floors...try srubbing with boiling water first before you buy buckets of chemicals.