Jephte I am inclined to think that the reason Paul is labelled a eunuch is because of this scripture Matthew 19:12 "For there are some eunuchs, which were so born from their mother's womb: and there are some eunuchs, which were made eunuchs of men: and there be eunuchs, which have made themselves eunuchs for the kingdom of heaven's sake. He that is able to receive it, let him receive it." I believe Paul falls into the last category, for the sake of the kingdom he lived a single life and if you read more of 1 Corinthians you will understand his reasoning. I would also advise you reading Matthew 19 from the beginning to gather the context. Eunuch can possibly be understood to mean devoid of sexual desire (my own thought) and I say this because one cannot be physically castrated from the womb but one can surely be born with limited or even no interest in the marriage bed.