Maybe "femtosecond" was used by Danish scientists in the 1800's or something, but it's definitely not a word that was common in another language and then import

Maybe "femtosecond" was used by Danish scientists in the 1800's or something, but it's definitely not a word that was common in another language and then imported into English. Worth noting that by the percentages here fewer than 50% of males surveyed were familiar with it.