This is really a good question, and it seems pretty well established that this term indeed appears on blades of mid 19th and into 20th century Germany; also that it is often mistaken for a makers name.
According to John Walter in "Sword and Bayonet Makers of Imperial Germany" blades were designated 'eisenhauerklinge' or 'iron cutter' as a declaration of quality, with similar terms in Belgium and a number of other countries.
Jean Binck had noted (2003) that it was a practice of early Passau swordsmiths to test blades by placing iron wire on a piece of wood, so its not as if the blade was to cut into iron plate. It does not seem that the term itself was used on blades until the 19th century. It is important to note that the quality of sword blades was obviously of key importance, and this implied guarantee was typically the purpose of the trade and guild markings which became so widely copied, the wolf and sickle marks among the best known.
In the latter 18th century, there was considerable competition between English swordsmiths and the imported German blades from Solingen which brought about what became known as the 'sword scandals' colloquially.
One of the main proponents for the English cause was Thomas Gill, who began marking his blades in 1788 with 'warranted never to fail', with several other makers following with variations of the phrase.
The imported German blades, aside from those marked by importer JJ Runkel, were often unmarked. The practice of these warranted phrases or the word alone seems to have carried into about the end of the Napoleonic Period on English sword blades, and by the mid 19th century the advent of proof marks took the place of these warranty notices on British swords.
It does seem quite plausible that the German use of this pronouncement of power or quality may have evolved out of the conflict mentioned, or simply as noted, a marketing device.
Other examples of pronouncing or guarantee of blade quality in terms would be that of Andrea Ferara on well known Solingen blades, typically for Scotland. It has been suggested by a number of arms writers through the years that this may be a term, 'Andrea =true, trustworthy; Ferara= iron', rather than a name..obviously the subject of ongoing dispute.
I once spent a great deal of effort having a Manchu inscription of only several characters translated (not many out there reading this
from a blade on a willow leaf sabre......hoping for something meaningful, it simply expressed 'tempered steel' .......apparantly significant note of quality in the 18th century in China in this same fashion.