Hello again. I am sorry because I could not shorten the reply.
The question which is also the title of this thread was answered to a large extent in the posts #3, #7 and #9. However the discussion has gone on along with 66 posts. In the post #1, I also stated that the word “Dick” is used as a male first name but also added that it has additionally a vulgar meaning. This was why it seemed strange to me. Because I previosly knew it just as an ordinary male name. I don’t remember exactly when I learned that it has also a vulgar meaning. Needless to say that there are a vast amount of media in text , picture, audio or video formats of obscene content involving it. I don’t want to disturb you with nasty examples. This reality can be thought as likening the given first name to a dress having a permanent stain on it. You can wear this dress if you don’t care the stain on it.
Perhaps this analogy is one of the disturbing points that some forum members have been missing or ignoring. In other words if the male name "Dick" was a dress, the noun “dick” with vulgar sense would be a terrible stain polluting it. Noone would like to wear a dress with a bad stain on it.
It seems that the way the nickname "Dick" of the legal first name "Richard" used in such a nasty context is an unfortunate reality. People can not change this reality but they can refuse using the problematic nickname and always prefer to use the legal first name “Richard”. I would wish that no vulgar connotation and context about this nickname were existent in English.
I got the main idea in your last paragraph. However I must correct some points. The Turkish word “Erdoğan” is a compound name by combination of the two Turkish words “er” and “doğan” and used as both first name and surname but mostly as surname. The word “er” can mean (1) early (2) private / soldier in an army (3) male person and the word “doğan” can mean (1) born (adjective) (2) the bird hawk. The compound surname “Erdoğan” can mean (1) “early born” and (2) “someone who was born to be a soldier/private”. It has got no vulgar connotation. Of course when I hear the surname “Erdoğan”, I don’t firstly think of these meanings. However the case for the nickname “Dick” is rather different. Since it has a vulgar connotation, someone can think of this connotation eventually.
Thanks for your contribution anyway.