How do we determine what a word means in the Bible? This simple question has a complicated answer!
(1) Many words have one meaning and no great controversy attaches to that meaning.
(2) Some words have more than one meaning so the question arises what meaning the word has in verse X (compared to verse Y). The answer will often be determined by the context (what the whole verse says, what the verse means in the context of a larger passage, etc). Sometimes the answer is indeterminate (i.e. scholars and translators disagree). Porneia is one such word.
(3) A few words are unique to the Bible so working out what they mean can involve much argument because usage of the word in other literature cannot be cited for comparative purposes.
(4) Some words appear to have a (slightly) different meaning in the Bible compared to usage outside of the Bible; some words in one part of the Bible are used in a standardized manner, but in another part of the Bible are used in a new way; in some instances this variation is within one book of the Bible. Arguably this last phenomenon occurs with porneia in 1 Corinthians.
Something tempting can happen within the complexities of seeking a word's meaning: we can (IMHO) become over enamoured with how words are used in literature outside of the Bible. On the premise that the Bible writers could develop their own meaning for a word, we need to be cautious about the weight we put on word usage in other literature. (One criticism I have of Haller's book is that he places a lot of weight on word usage (or non-usage) in rabbinical literature: there is value in considering this literature, but it is literature which (a) is not the Bible (so usage may be different, especially in respect of the New Testament), (b) difficult to date so that citing Rabbi X re word Y may, at best, give us the usage of a word in an era after the closure of the New Testament. What is surprising in this amount of weight being placed on rabbical literature is how little weight is placed on New Testament scholarship by Christians).
Enough for now.