Examples have been found from Roman times and museums have examples circa 1200 when, the Muslim engineer Al-Jazari documented a combination lock.
CC-BY-SA 3.0 Sigismund von Dobschütz
Perhaps the name was popularised since 1909 because it was patented as a physical object, not a mathematical concept.
Thus it's the way that "word combination" locks the usage.
My invention is an improvement in locks and consists in certain novel constructions and combinations of parts hereinafter described and claimed.
The object of the invention is to provide a combination padlock, of simple and cheap construction, which will be strong and durable, and not liable to get out of order easily, and in which the combination may be easily changed.
Origin of combination 1350–1400; Middle English combinacyoun (
Middle French ) < Late Latin combīnātiōn- (stem of combīnātiō
It is simply the combination of characters that let us pick holes in the term.