Greetings from the Academy of Saint Gabriel!
Here is the information we have found on your proposed 15th century Spanish name.
We did not find any evidence that "Tarsiana" was used in Spain as an actual woman's given name. We do have evidence that it was used at least as an alias in literature of the period, and that it appears to be closely related to several names that were used.
In the medieval lyric tradition, women are often addressed in poetry by aliases rather than by their actual names. Often, these aliases were based on the city or region that the lady is from. It is possible that the "Tarsiana" in your source is an alias based on the lady's area of residence.
We did find some secondary evidence that Tarsiana might be a reasonable form. There is a group of Italian given names deriving originally from the region of Tarsus; they include Tarcisio, Tarciso, Tarcidio, Tarcisia, and Tarcisa (1). There were several Spanish forms from the same origin, including Tarsicia, Tarsici, and Tarsila; our source specifically equates these names with the Italian "Tarcisio"(2). The root, "Tarsi-," has had various modifications done to it; adding the suffix "-an(a)" would not be unusual in this context. However, although it is possible that "Tarsiana" might have been a given name, we have no evidence that it was ever used as such by an actual, living person.
Another source (3) gives TarsicióTarsicia, Ta'rsilóTa'rsila and its variant, TarsilióTarsilia as the ecclesiastical Latin forms of Tharsicius, from the Greek name Tharsikios, a derivative of "tharsos," meaning "brave" or "valorous." The source mentions two 3rd century male saints, one Roman, one Alexandrian, and a 6th century French female saint bearing these names. Also, Tarsila and its variant, Tarsilia, are ecclesiastical Latin names; a virgin saint, Tarsila, was Gregory the Great's aunt. We believe that any of these names might have been used by a Spanish woman in the Middle Ages.
In an article on Leonese names, we did find four instances of "Tarasia" used as a given name between 1001 and 1200 (4). "Tarasia" also appears in another source as an actual person's name from 1088 (5). Although it is not the same as "Tarsiana," it is certainly close, and clearly documentable.
You also asked whether it would be possible to register only a single given name. Actually, except in very particular circumstances, names recorded in our period of study very rarely consist only of a given name. By the 15th century, it would be very unusual for a person to have only a single given name. In any case, the College of Arms requires at least two elements in every registered name. Therefore, although you can use "Tarsiana" or "Tarasia" alone, you will not be able to register only "Tarsiana" or "Tarasia" as your persona's name.
We do not have a great deal of information about Spanish Romany naming practices. The best we have been able to learn about Romany naming is that they used private names in their own language, which were not revealed to outsiders. They had public names in the local language, which followed the prevailing naming practices; thus, you would be looking for a normal Spanish name for your period.
Given your persona, we are assuming that you would not want a locative (city- or region-based) byname; a patronymic (a name based on your father's name) would be more appropriate. Some of the more common ones are Martinez, Perez, Nun~ez, Mun~oz, Fernandez, Rodri'guez, Juanez, Gonzalez, and Diaz (4), as well as Sa'nchez, Lopez and Herna'ndez (6). We believe that Tarasia, Tarsicia, Ta'rsila or Tarsilia coupled with a patronymic byname, could have been used in Spain during our period of study.
You asked whether your name documentation should match your persona's period. For purposes of historical re-creation, it is best to choose a name that you know was used in the time and place where you set your persona. The College of Arms does not pay attention to personae; rather, it is concerned that the name submitted is correct for some time in our period. You are the one who must be satisfied that your name matches your persona.
We are always searching for more sources for our reference library; as it is, our resources on Spanish naming practices are limited. We would appreciate it if you could tell us where you found "Tarsiana," and also what evidence you have about Romany name practices in Iberia during our period of study. The more information we have, the better we can assist other people interested in these areas.
We hope that this has been helpful, and that we can continue to assist you.
Tangwystyl verch Morgant Glasvryn, Arval d'Espas Nord, Elsbeth Anne Roth and Talan Gwynek contributed to this letter.
Giulietta da Venezia
Academy of S. Gabriel
(1) DeFelice, Emidio, _Dizionario dei Nomi Italiani_ (Milan: Arnoldo Mondadori, 1986).
(2) _Gran Diccionario de los Nombres de Persona_ (Spanish).
(3) Tibo'n, Gutierre. _Diccionario Etimolo'gico Comparado de Nombres Propios de Persona_ (Union Tipografica Editorial Hispano Americana: Mexico).
(4) Pascual Martinez Sopena, ed., _Antroponimia y Sociedad_ (Universidade de Santiago de Compostela and Universidad de Valladolid, 1995).
(5) Di'ez Melco'n, R.P. Gonzalo, _Apellidos Castellano-Leoneses_ (Universidad de Granada, 1957).
(6) Luis Romera Iruela and Ma. del Carmen Galbis Di'ez, _Catalogo de Pasajeros a Indias, Siglos XVI, XVII, y XVIII_ (Sevilla: Archivo General de Insias, 1980).