the term "pushout"

[Peter Freyd <pjf@seas.upenn.edu>]

Peter Johnstone asks who coined  the term "pushout".

On page 156 of Abelian Categories I wrote (43 years ago!):

  The word "pullback" and the ubiquity of the concept I learned from
  Lang, who also pointed out the pullback theorem and its importance.
  I plead guilty to "pushout"...
            (www.tac.mta.ca/tac/reprints/articles/3/tr3abs.html)

MathSciNet lists Alex Heller's review of Abelian Categories as its
second oldest use of the term "pullback" and its oldest use of
"pushout". (Its first use of "pullback" is in Alex's review of John
Gray's 1962 paper "Category-valued sheaves" -- no the stalks were not
categoies.)

It was my impression that Serge Lang invented the term "pullback" (his
term for the dual notion was "co-pullback"). Note that I refrained
from stating this impression. But I do claim to have invented the term
"pushout" -- indeed, I've been know to cite this as my most visible
contribution to mathematics.