The spelling of the word "Brestsummer" can be explained through its phonetic transcription in IPA. It is pronounced as /brɛstˈsʌmər/ and can be broken down into two parts - "Brest" and "summer". The first part refers to the French city of Brest and is spelled with a "r" to differentiate it from the English word "breast". The second part refers to the season, "summer". Therefore, "Brestsummer" is a word that combines the French city and the season to represent a specific time and place.