It's spelled polyurinstain, or polyurinate... but you were close enough. Shellac is still the preferred finish amongst the devoted restorers of A&C style bungalows (seeing as that's what most were finished with). It will not stand up to animal pee, nor spills of strong bases like ammonia. It is, however a dream to apply (a wool bat on a mop handle works great). The alcohol fumes aren't bed because they dissipate quickly - no extended outgassing period as with oil varnishes. Probably the cheapest way to go is to use Zinsser's Seal Coat, cut 1:1 with fresh 200 proof denatured alcohol. It's work it to get that stuff from a chemical supply house versus the stuff from the hardware store.
Careful sanding of the floor is the most important (and arduous) step... but regardless of the finish, ya gotta do it anyways.
Humbly submitted, O'Deen