one quintillionth part of; the factor 10: attosecond
Origin of atto-; from Danish atten, eighteen ; from Old Danish attan ; from atta, eight + -tjan; akin to Old English -tyne, -teen
One quintillionth (10−18): attotesla.
Origin of atto-From Danish or Norwegian atten, eighteen, from Old Norse attjan; see okt&omacron;(u) in Indo-European roots.
From Danish atten (“eighteen”).