http://www.vikingsword.com/ethsword/...%20Machete.pdf
When I wrote this article on the espada ancha, part of the theme concerned not only the use of this term for these basically utilitarian short swords, when they were known locally only as 'MACHETE'...but the history of their evolution and use.
The modern application of the term ESPADA ANCHA for them seems to have come about c. 1965 when historian Odie Faulk was translating from the regulations for colonial soldiers of I believe 1772. In these regulations it was ordered that the mounted soldiers were to continue carrying the 'espada ancha', in this case referring to the 1728 dragoon sword (known in English as the bilbo).
Mr. Faulk assumed, as he knew of the preference of the colonial mounted troops for the short swords, which they typically wore on the trails, so he thought the espada ancha in the regulations meant these rather than the 'bilbo' (which was meant in the wording) .
Faulk was a close colleague of Sidney Brinckerhoff, who in 1972 with Pierce Chamberlain wrote "Spanish Military Weapons in Colonial America 1700-1821". In this, virtually the only reference book on Spanish colonial weapons, Brinckerhoff carried forward this application of the term espada ancha for these 'machetes' . As Woodward (1946) notes, even into the 20th century these short swords have been known as machete.
Historian/artist David Rickman confirmed this situation to me in conversations while working on this article (for which he did the art work), and he had been told this by Mr. Brinckerhoff.
It does make sense that Spanish fencing manuals would not be overly specific in descriptive names for sword types, and the term espada would of course be collectively used. As noted the term 'bilbo' was entirely of English origin which arose in the late 16th century for fine Spanish swords which came out of the northern port of Bilbao.
The colloquial term for these, 'boca de caballo' ,also was simply a colorful term used informally .
The term espada ancha used in the regulations previously noted was intended to specify continuing the use by colonial mounted troops of the LARGE SWORD (=espada ancha) of regulation use as opposed to the smaller swords (machete) which were privately made locally and clearly non regulation.