The phrase 'spick-and-span' has no alternative sexual connotations in and of itself. I have no idea why one men's magazine in the 1950s chose the phrase for its name, but I can see no other 'questionable' uses of the phrase in the first few pages of my google of the idiom. Keep in mind that almost any English phrase (and this no doubt applies to all languages) can be used by those whose minds are set in that way.
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