(Chapter 19) Footnote 72:

Xiphoid, Latinized as ensiform. The Greek term is usually applied only to the xiphoid cartilage at the end of the sternum, but in some passages in De anatom. adm. (496.11, 516.5, 549.14, 655.10) it appears to refer to the sternum generally; see also De ossibus 764.18, which Vesalius probably has in mind here: “The sternon as a whole is like a sword, hence some call it the xiphoid bone” (tr. Singer 1952, p. 773).