Hof, Mössenböck and Pirkelbauer (in their 1997 paper Zero-Overhead Exception Handling using Metaprogramming) affirm that the concept of exceptions was suggested in the seventies, referring to John B. Goodenough's 1975 Exception handling: Issues and a proposed notation paper in the Communications of the ACM. In it he conflates modern exception handling with the general idea of registering callbacks, and his proposed notation looks more like modern Attribute metadata specifications than
try/catch, but it (or at least its section 2) is a great overview of the state of exception handling in the mid-seventies.
Perhaps of note is also the
raise/rescue mechanism in Alef, which one can view as a primitive form of
catch blocks, lest we think they sprang fully-formed from Stroustroup's brow like Athena from Zeus's.