When was the "arrow notation" $f: X \to Y$ for functions first introduced? Who introduced it and with which motivation?
I ask this question in order to understand whether it was, in part, this notation to suggest that there could be "higher morphisms" (in analogy with oriented paths and homotopies between them, and homotopies between homotopies and so on), or if it went the other way around (with category theorists first realizing that many constructions involving paths and homotopies thereof in Homotopy Theory could be generalized to other more abstract settings, and then setting up a notation that suggested the analogy "1-morphisms $\sim$ paths").
Best Answer
Despite the claims reported from Wikipedia and the “Earliest Uses” site, this notation certainly started much before Hurewicz-Steenrod (1940; 1941) or Ore (1935, p. 416; 1936) for, respectively, Domain-to-Codomain and Argument-to-Value arrows.
1. Domain $\to$ Codomain (as in the question proper):
Scholz (2008, pp. 883-884) describes manuscripts and lecture notes of Hausdorff (1933):
I’m not finding any set-to-set arrows in Weyl (1925). But he has at least one in (1931, p. 267), and van der Waerden (1930; reviewed by Ore in 1932) has indeed, e.g.
McLarty (2006, p. 200) argues that the first one at least was only “a prescient typographical error” for a Nœther tilde $\sim$. But I’m not sure I buy this, as there are more and this is unchanged in later editions (1955, 1971, 1993).
2. Argument $\to$ Value (nowadays written $\mapsto$, with other antecedents):
These are much older. All references above have many, but the earliest I’ve seen are shaped $\rightarrowtail$ and occur in perhaps the earliest commutative diagram, by Eduard Study (1891, p. 508). The next are again in papers of Study, (1905):
and (1906, pp. 493-496, 511-516). Blaschke (1910a, 1910b) adopts them throughout, as do books by Blaschke-Study (1911/13, pp. 15, 17, 23, etc.), Weyl (1913, e.g. pp. 32, 50, 54, 139, 159), Speiser (1923, e.g. pp. 38, 88, 103), or again Study (1923). There, §1 “Grundbegriffe und Zeichen” (p. 16) sounds much like he’s claiming the notation, while crediting Wiener (1890) for another: