Rule of Three

[Arnold M. Zwicky]

a commentator on NPR's Sunday Morning Edition today (2/8/04) claimed
that the three most important (electoral) issues in michigan are:
"Jobs, jobs, jobs."

this is (i think) a play on the real estate cliche that the three most
important considerations in buying a house are: "Location, location,
location".  location-location-location itself has been extended to a
great many domains besides real estate; to appreciate this, google on
"location location location" and sample some of the roughly 218,000
sites listed.

in any case, there's a formula here:
   The three most important Xs in Y are: Z, Z, Z.
(conveying something like 'the only really important X in Y is Z').

i've been calling this, in my own  mind, the Rule of Three, but perhaps
somone has studied it already, and given it a name?  has anyone
assembled some collection of instances of the formula?  (they are all
over the place.)  has anyone looked at the history?  (is
location-location-location in the real estate domain the earliest
exemplar in english?  in any case, what's the earliest citation for an
exemplar?)

this is *not* an invitation for people to supply their recollections of
exemplars of the formula, though citations from printed sources or data
collections, especially of some age, would be welcome.

arnold (zwicky at csli.stanford.edu)