copperfasten

Etymology
. From of ship hulls (to protect from damage by marine organisms. Originally copper sheathing but non-copper bolts were used, leading to corrosion. Later copper bolts (fasteners) were also used, eliminating corrosion issues. Literal sense from 18th century, metaphorical sense attested 1948.

Verb

 * 1)  To protect the timbers of (a ship) with plates of copper secured with copper nails or bolts.
 * 2) * 1796, The Hull Advertiser, 9th July 1796:
 * She is copper-fastened and copper-bottomed, and a remarkable fine ship.
 * 1)  To reinforce, strengthen; to make permanent, embed.
 * 2) * 1948, The Evening Independent, November 1948:
 * We had some striking examples of what happens when a guy gets so big for his britches that any pal of his is automatically a copper-fastened genius.
 * 1) * 2010 “Supreme Court rules on law translation”, RTÉ News, May 6, 2010:
 * This brings to an end a ten-year campaign by Pol O Murchú and other Irish language activists to copperfasten rights to have Irish language legislation made available

Usage notes
Particularly used attributively, as (less commonly, ).

Originally (in literal sense) an intensifier of, meaning not only that the plates were copper, but the fasteners too. In meaning close to, but emphasis on security and lack of ambiguity (compare ), rather than on certainty and trustworthiness.