There are many indicators that the name Sonzino may be of Jewish origin, emanating from the Jewish communities of Spain and Portugal.
When the Romans conquered the Jewish nation in 70 CE, much of the Jewish population was sent into exile throughout the Roman Empire. Many were sent to the Iberian Peninsula. The approximately 750,000 Jews living in Spain in the year 1492 were banished from the country by royal decree of Ferdinand and Isabella. The Jews of Portugal, were banished several years later. Reprieve from the banishment decrees was promised to those Jews who converted to Catholicism. Though some converted by choice, most of these New-Christian converts were called CONVERSOS or MARRANOS (a derogatory term for converts meaning pigs in Spanish), ANUSIM (meaning "coerced ones" in Hebrew) and CRYPTO-JEWS, as they secretly continued to practice the tenets of the Jewish faith.Our research has found that the family name Sonzino is cited with respect to Jews & Crypto-Jews in at least 3 bibliographical, documentary, or electronic references:
The Amsterdam Municipal Archives possess a complete set of registers of intended marriages from 1578 to 1811, the year when the present Civil Registry was started. Between 1598 and 1811, 15238 Jewish couples were entered in these books. Both the number of records and the volume of data that may be extracted from them are unprecedented.
This register is from the manuscript record preserved in the Archives of the Spanish and Portuguese Jews' Congregation of London named "Sahar Asamaim" transcribed, translated and edited by the late R.D. Barnett, with the assistance of Alan Rose, I.D. Duque and others; There is also a supplement with a record of circumcisions 1679-1699, marriages 1679-1689 and some female births 1679-1699, compiled by Miriam Rodrigues-Pereira. The register includes surnames of those circumsized as well as the names of their Godfathers & Godmothers.
Around the 12th century, surnames started to become common in Iberia. In Spain, where Arab-Jewish influence was significant, these new names retained their old original structure, so that many of the Jewish surnames were of Hebrew derivation. Others were directly related to geographical locations and were acquired due to the forced wanderings caused by exile and persecution. Other family names were a result of conversion, when the family accepted the name of their Christian sponsor. In many cases, the Portuguese Jews bear surnames of pure Iberian/Christian origin. Many names have been changed in the course of migration from country to country. In yet other cases "aliases", or totally new names, were adopted due to fear of persecution by the Inquisition.