The history of decussate leads us back to the intersection of decem, a word meaning "ten," and ass-, a form that refers to a unit of weight and specifically to a copper coin cut to a half-ounce. In the Roman numeral system the number 10 is represented by X, an intersection of two lines. A man named Sir Thomas Browne coined decussate in the 17th century to discuss the crossing fibers that make up human anatomy-for instance, skin tissue. The word continues to be found primarily in scientific contexts today.
Word History
Etymology
Latin decussatus, past participle of decussare to arrange crosswise, from decussis the number ten, numeral X, intersection, from decem + ass-, as unit — more at ace