Evicción and “eviction” are truely false cognates. En English “eviction” denotes “the act or process of legally dispossessing a person of land or rental property” (Black’s Law Dictionary). The corresponding term in Spanish is desahucio, as in desahucio del inquilino por impago del alquiler (“eviction of the tenant for failure to pay the rent”) or desahucio del arrendatario por expiración del contrato de arrendamiento (“eviction of the tenant upon expiration of the lease”).
In contrast, in Spanish evicción refers to the loss of title to or possession of property due to a third party’s superior title. Thus, in the context of real estate sales, the often-mistranslated expression saneamiento por evicción denotes a type of “warranty of title,” “warranty of good title” or “warranty against loss of title,” i.e., the seller’s guarantee to the buyer he will enjoy undisturbed legal possession of the purchased property (posesión legal y pacífica de lo vendido). If, after the sale, a court rules that another person holds superior title (mejor derecho) to the property, the seller must compensate the buyer as established by law.* Likewise, in the context of lease agreements saneamiento por evicción constitutes a “warranty of quiet enjoyment,” that is, the lessor’s guarantee that the lessee will enjoy undisturbed possession (que no será perturbado en su posesión) of the premises for the duration of the lease.
*In that regard, buyers’ rights in Spain are explained in detail in this article on Saneamiento por evicción en la compraventa: http://cortesyperez.blogspot.com.es/2012/09/el-saneamiento-por-eviccion-en-la.html