Spanish Surnames
The particle "don" may indicate either if a person is noble or if he is owner or master. Also applied as a way of distinction in any conversation, an employee could call his employer "don". Only in ancient times it was used as a sign of nobility. It's always written without capital letters except in the beginning of a sentence.
The Spanish could- until some centuries ago- use a surname chosen from those of their ancestors or of the place they belonged to. In that way, a person having Treviño, Campos, Avellaneda, Quesada, Garzón, Ávalos, Astudillo y Carvajal as his grandparent's surnames, could use any of them as main surname. Women would frequently carry the surname of a grandmother or their mother. Yet another way of choosing a surname could be, for example, adding the surname of the mother to the father's (something still used). The way in which the surnames were added could vary but the most popular were : Name, father's surname, mother's, grandmother, grandmother, great grandfather... etc. and that of motherly discrimination (Father's, mother's, grandmother's, great grandmother's, great grandmother's...). In that way; supposing the great grandparent's surnames were Treviño, Casas, Campos, Toledo, Avellaneda, Gache, Quesada, Dávalos, Garzón, Jiménez, Ávalos, Paz, Astudillo, Páez, Carvajal y Pena; the person could either be called: José (+as many names as desired, now limited to 3 in many countries, Argentina for example) Treviño Garzón Avellaneda y Astudillo or, in a second way: José (+names) Treviño Garzón de Avellaneda Campos y de las Casas. That if he was to use all the surnames.
The use of 'de' (of), 'del'-'de las' (of the) and 'y' (and) depends on the will of the beholder. Originally, the surnames having 'de' used it as an alternative particle that could be removed or added depending on how it appeared to the owner. Of course, in the first times, noone would think of adding the particle 'de' to a surname indicating a profession (ex. Herrero, Herrera meaning Smith being written as 'de Herrero' or 'of Smith') but it was widely used among places ('de Triana', 'de Toledo', 'de Baeza') or indicating a house ('de Cabrera'), in spite of the surname of the house being the name of a place. This is not seen in English Surnames, when the 'of' is only used for indicating places either in ancient times or at the highest levels in the Peerage (Eleanor of Aquitaine, William of Ross).
Of course, going back to the Spanish case, the 'de' can be used even if the person in question uses only one surname (José de Treviño) or more than once (Manuel Alvarado Páez Gutierrez de Molina y Gache de Avellaneda) but the 'y' cannot since, meaning 'and', is to be placed in an enumeration (Juan del Pozo y Silva, José del Pozo Silva y Garro, Juana Rivero y Kelly, Francisco Cabo y Colina Reboria y Álvarez).