In Case You Wondered

Wandering around the Wikipedia. Those Romans had a word for everything and the meanings carried social, emotional and political overtones often as not:

Even then, there were still notable taboos: in pre-Christian ancient Rome sexual acts were generally seen through the prism of submission and control. This is apparent in the two Latin words for the act: irrumare (to penetrate orally), and fellare (to be penetrated orally). Under this system, it was considered to be abhorrent for a male to be in any way penetrated (be controlled) by another person of lower social standing during sex. This same logic also allowed a man to receive fellatio from a woman or another man of lower social status (such as a slave or debtor), because the man would be directing the actions of the person of lower rank. The Romans regarded oral sex as being far more shameful than, for example, anal sex -- known practitioners were supposed to have foul breath and were often unwelcome as guests at a dinner table. The women of Lesbos, ironically enough, were believed to have introduced the practice of fellatio, and it is said that they used to whiten their lips as though with semen.

So, whereas in Greece, where there was a tendency to see the person "performing" oral sex as active and the "receiving" party as passive, in Roman times fellatio and cunnilingus were perceived to be a passive and therefore shameful act for any man to perform, and oral sex between members of low social standing groups was considered superfluous and was often viewed as taboo. Therefore performing any type of oral sex was considered to be a passive (as in submissive) act while receiving oral sex was viewed as an active (as in controlling) act. The practice was taboo for public health reasons, as well. In Rome, the genitals were considered to be unclean. Oral sex was thought to make the mouth dirty, and (ultimately) to present a public health risk.