Raise your eyes in the Gramont street, in front of the n°20. You will notice on one side of the street a street plate showing "RUE DE GRAMONT" with a single "M" and almost in front of it, on the other side, a street plate showing "RUE DE GRAMMONT" with 2 "M"! So, what plate do you think is correct ? Where is the truth ?
In fact the Faculty of Sciences has solved this historical debate in 1930 on september 13th! Indeed at this date, the authorities of the "Ville de Paris", based on the recommandations of the "Old Paris town Commission," aknowledged that there had been a spelling mistake by the administration and that the "Rue de Gramont" should be spelled with only a single M.
The mistake had been made in 1765, the year when the street had been opened through the gardens of the "Hotel de Gramont". It was at that time, the historical house of the Duc de Gramont (with a single M). On september 13th 1930, the Paris City Hall had eventually rectified an administration mistake 165 years old!
As had been underlined as soon as in 1868 in the "Courrier de Vaugelas" newspaper, this mistake was unfairly assigning the historical past of the street to the Grammont (avec 2M) family, coming from Burgundy and not to Gramont (with a single M) family coming from the Navarre. The Old Paris commission had estimated in 1923 "(it would be) fair that the Gramont house, that has had two France Marshalls, several cardinals, several generals (...) would take it seriously the correct orthography for the fame of the Name be rectified".
In 1930, the recognition of the historical and heroic acts achieved by the Gramont family members for the sake of royalty was eventually official.
The spelling of the rue de Gramont in the Paris 2nd arrondissement is now with a single M. This adjustment has naturally led to the change of our hotel name... That is the reason why, some old invoices or newspapers ads of the Hotel Gramont , still show "HOTEL DE GRAMMONT", as in the page underneath found in the 1878 "Indicateur Marseillais" (source Gallica.bnf.fr).