Learn English – How was sexual intercourse referred to before ‘sex’

Bowdlerization is clearly much broader in scope, as it refers to the general editing of any text to remove potentially offensive content.

The substitution of letters in profanities with asterisks or other characters was a practical solution for U.S. and U.K. publishers in the 20th century, devised to avoid the possibility of prosecution for the violation of obscenity laws.

In the U.S., 7 words were considered profane and their use forbidden in radio, television and most sorts of printed media. Those were: shit, fuck, piss, cunt, cocksucker, motherfucker, tits. These words are still not used on the major American television networks or in some publications (national newspapers such as the "New York Times", etc.).

One term invented in 1980 to describe textual symbols meant to represent profanities is "grawlix/grawlixes". Other suggestions for the same thing are "obscenicons" or "maledicta". These refer to e.g. old comic strips in which the dialog bubbles of characters sometime contain expressions like "@#*!%!", meant to represent a profanity.

See http://languagelog.ldc.upenn.edu/nll/?p=2457

Miscegenation was coined in the US precisely to condemn such relations. Its historical context was in arguments in defense of slavery: The possibility of mixed-race marriages or sexual relations being projected as an outcome so horrible that it was good that slavery was preventing it (of course slavery led to a lot of mixed-race children too, but that was not talked about) - and anti-miscegenation laws banning marriages and sexual relations between different races that existed in the US until 1967 when the federal Supreme Court ruled the last such laws to be unconstitutional.

The reason miscegenation was taken as applying particularly to the marriage, sexual relations or offspring of white people and people of other races, is that this was seen as a problem to the white racists that coined the word. Indeed while some laws did in fact specifically ban black people from marrying people of any other race (as the race deemed lowest in the racist hierarchy such people believed in) and some blocked people of non-white races from marrying each other, the overall focus was on "protecting the white race" from the perspective of white racists.

There is no parallel word because there wasn't a powerful group of black people who spoke English as their primray language, feared inter-racial marriages and spent centuries enacting and enforcing laws to prevent it, to coin such a word.