[103] Why do they call children of unknown fathers spurii?[240]
Now the reason is not, as the Greeks believe and lawyers in court are wont to assert, that these children are begotten of some promiscuous and common seed: but Spurius is a first name like Sextus and Decimus and Gaius. They do not write first names in full, but by one letter, as Titus (T.) and Lucius (L.) and Marcus (M.): or by two, as Tiberius (Ti.) and Gnaeus (Cn.): or by three, as Sextus (Sex.) and Servius (Ser.). Spurius, then, is one of those written by two letters: Sp. And by these two letters they also denote children of unknown fathers, sine patre,[241] that is “without a father”: by the s they indicate sine and by the p patre. This, then, caused the error, the writing of the same abbreviation for sine patre and for Spurius.
I must state the other explanation also, but it is somewhat absurd: They assert that the Sabines use the word spurius for the pudenda muliebria, and it later came about that they called the child born of an unmarried, unespoused woman by this name, as if in mockery.