The blogger behind Life in Translation has sticky notes to remember which party is which:

Similarly, it ought to be enough that these terms are in my termbase but somehow it isn’t. And so three sticky notes (physical paper, not electronic ones) live on the edge of my screen.
Arrendadora – LESSOR
Arrendatario – LESSEE

Franquiciante – FRANCHISOR
Franquiciado – FRANCHISEE

Fiduciaro – TRUSTEE
Fideicomitente – SETTLOR/TRUSTOR
Fideicomisario – BENEFICIARY/TRUSTEE

I suggest adding MORTGAGOR and MORTGAGEE