"On teaching mathematics" by V.I. Arnold:
Prof. M. Berry once formulated the following two principles:
The Arnold Principle. If a notion bears a personal name, then this name is not the name of the discoverer.
The Berry Principle. The Arnold Principle is applicable to itself.
It is also interesting, how Arnold's Principle can be applied to Arnold's works.
1) Arnold's Problem (problem 1993-11 from "Arnold's Problems" Springer, 2005) on statistical properties of finite continued fraction was essentially solved by Lochs in 1961 (32 years before Arnold’s conjecture, see "Statistik der Teilnenner der zu den echten Brüchen gehörigen regelmässigen Kettenbrüche", Monatsh. Math., 1961, 65, 27-52).
2) His question about weak asymptotic for Frobenius numbers (problem 1999-8 from "Arnold's Problems" Springer, 2005) was asked earlier by Davison (only for three arguments, but in fact the question is the same, see "On the linear Diophantine problem of Frobenius", J. Number Theory, 1994, 48, 353-363)
3) In the article "Geometry of continued fractions associated with Frobenius numbers" (Funct. Anal. Other Math., 2009, 2, 129-138) he almost rediscovered Rodseth's formula for Frobenius numbers.