1670s (plural), "teen-age years of a person," formed from -teen taken as a separate word. As "decade of years comprising numbers ending in -teen," from 1889.
Entries linking to teens
-teen
word-forming element making cardinal numbers from 13 to 19, meaning "ten more than," from Old English -tene, -tiene, from Proto-Germanic *tekhuniz (cognates: Old Saxon -tein, Dutch -tien, Old High German -zehan, German -zehn, Gothic -taihun), an inflected form of the root of ten; cognate with Latin -decim (source of Italian -dici, Spanish -ce, French -ze).