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 āttjān ; see oktō(u) in Indo-European roots.
From Danish atten (“eighteen”).