So much interesting questions about club shields. I'm not fond of that, but I like and admire heraldry. The English are far away from us. Their 5th or 6th division clubs have incredibly beautiful crests.
It represents the "berceau royale," or royal cradle, springing from a blazon/coat of arms representing the royal town of Saint-Germain en laye ("royal" because somebody royal lived there regularly). A blazon is the actual written description of a coat of arms, a royal one of which the above town claimed as early as 1638. From the website, where, if you look in the upper-right corner, you will see the royal blazon/coat: ...Many old documents referring to the city of Saint-Germain-en-Laye are stamped with the 3-fleur-de-lis royal seal bearing the arms of France. This "signature" identifies Saint-Germain as a royal city, first of all because it was part of the royal domain, and secondly, because it served as a residence for the royal family. • As early as the period of the "Restoration" of the Bourbons, the city had wanted to use the seal bearing the arms of France (and of Navarre), arguing that it was justified in doing so because of Saint-Germain-en-Laye's past and its status as a royal city. Unfortunately, the city was unable to substantiate its claim at the time. On August 11, 1816, the Ministry of Justice proposed a blazon. Thanks to a letter patent dated August 17, 1820, King Louis XVIII granted the city a blazon bearing a cradle and the date September 5, 1638, in honour of the birth date of his grandfather, Louis XIV. • You can find the different elements of this blazon, along with an oak leaf symbolizing the forest, on the present-day Saint-Germain-en-Laye logo. It was created in 2002 and continues to identify the city's many undertakings... Thus, PSG's logo has since about 1991 reflected "Paris" in its employment of the Eiffel Tower, and "Saint-Germain" in its use of the berceau royale, as reflected in a blazon/coat of arms for the town of Saint-Germain de laye. This also, of course, reflects primarily the merger of two clubs, FC Paris and Saint-Germain-en-Laye, into a new club similar to the way "United" in UK football parlance reflects the merger of two or more clubs into a new one (e.g., Manchester United, Newcastle United, etc.)