This was trademarked by Audio Devices in Stamford, CT, in 1971, which makes sense since the Commodore Datasette likely didn't exist until the Commodore PET was created in 1977. Commodore seemed to use both 'datasette' and 'datassette'. Perhaps Commodore registered the double-S spelling. Perhaps they were challenged by Audio Devices for using the 'datasette' spelling.
