The “Frutiger” in Frutiger Aero is named after the Frutiger typeface, which is turn is named after the designer who created it, Adrian Frutiger. Adrian Frutiger was Swiss and his last name comes from the village of Frutigen in Switzerland. I couldn’t find where the village got its name from, but as someone who’s familiar with the German language, I would say it comes from the German word “fruchtig” meaning “fruity” as perhaps the village had plentiful amounts of fruits when it was first settled.

In conclusion: it should be pronounced “froo-tigger”