teen (n.)

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).

also preteen, "just prior to one's teenage years," 1926, from pre- + teen. As a noun, "pre-teen person," from 1962. Sub-teen (1944) also was used.