I think you might be going at this the wrong way. Naughty words are naughty because they are used in a naughty manner, not because of what they actually mean, or used to mean. If we look at general swearwords, where they're taken from depends very much on culture. Where I am from, the bad, native swearwords are religious in theme: satan, hell, damn you etc. Swearwords realted to bodily functions and sex are much rarer, many borrowed from English actually. In Brussels, some use the word "architect" as a swearword. Considering some of the architecture there and the history of how those buildings came about, that is very understandable. Due to some of the architecture that have turned up where I live, I've started using "architect" as a swearword myself.
What I think you are looking for is euphemisms, inoffensive words being used as stand-ins for offensive words. Euphemisms is a rich source of new naughty words, as the offensive meaning "rubs off", and then the euphemism needs a euphemism of its own. You'd need some way of discovering words that mean soft, words for anything that resembles a stick, and words for temperatures above normal at least, but this is fascinatingly unpredictable really.
The simplest would probably be to find porn-sites in various languages, sort them on language, get the text-content and use that to train a learning spam-filter. (You'll need text from non-porn sites too). Then see if you can pick out words or preferrably several word-pairs or word-triplets from that that are good indicators of "porniness".
And now for the obligatory reference in this case ;)
Quang Phúc Ðông: "English sentences without overt grammatical subject", South Hanoi Institute of Technology, Hanoi, 1967
