The 'law of the instrument' was named by philosopher Abraham Kaplan (1962/1964) and has print ancestors to 1868, predating the wording popularly credited to Maslow (1966)

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The "hammer and nail" proverb — often attributed to Abraham Maslow — is older than Maslow's use of it and was formally named by someone else. Quote Investigator traces the figure back to an 1868 London periodical, then to the philosopher Abraham Kaplan, who set it out as a named principle in a 1962 conference speech and his 1964 book The Conduct of Inquiry: "I call it the law of the instrument, and it may be formulated as follows: Give a small boy a hammer, and he will find that everything he encounters needs pounding." Kaplan's coinage — "the law of the instrument" — is the term of art the popular Maslow attribution obscures.

Maslow's own contribution came later and in different words. His 1966 The Psychology of Science wrote: "it is tempting, if the only tool you have is a hammer, to treat everything as if it were a nail" — the "nail" variant, but not the phrasing that circulates under his name (see the wording popularly credited to him, which tracks a 1982 secondhand misquote instead). The earliest "nail"-bearing formulation in the genealogy predates Maslow too: it sits in a 1963 volume, one of whose contributors was Kenneth Mark Colby — the thread that carries the idiom into the history of AI at claim-hammer-nail-genealogy-runs-through-kenneth-colby-parry-creator.

The note belongs to the vault's standing interest in how attribution drifts toward the famous name — Stigler's Law of eponymy ("no scientific discovery is named after its original discoverer"), here applied to an aphorism rather than a discovery. Kaplan named the law; Maslow got the credit.