combining form Etymology: International Scientific Vocabulary, probably alteration of hepta-; from the fact that 1021 is the seventh power of 103 one sextillionth (10 -21 ) part of
ZEPTO-
Meaning of ZEPTO- in English
Merriam Webster. Explanatory English dictionary Merriam Webster. Толковый словарь английского языка Мерриам-Уэбстер. 2012