Some interesting parallels between the original Scheme and message-passing from "The First Report on Scheme Revisited" by Sussman and Steele
> We were very pleased with this toy actor implementation and named it “Schemer” because we thought it might become another AI language in the tradition of Planner and Conniver. However, the ITS operating system had a 6-character limitation on file names and so the name was truncated to simply SCHEME and that name stuck. (Yes, the names “Planner” and “Conniver” also have more than six characters. Under ITS, their names were abbreviated to PLNR and CNVR. We can no longer remember why we chose SCHEME rather than SCHMR—maybe it just looked nicer.)
> then came a crucial discovery. Once we got the interpreter working correctly and had played with it for a while, writing small actors programs, we were astonished to discover that the program fragments in apply that implemented function application and actor invocation were identical! Further inspection of other parts of the interpreter, such as the code for creating functions and actors, confirmed this insight: the fact that functions were intended to return values and actors were not made no difference anywhere in their implementation. The difference lay purely in the primitives used in their bodies. If the underlying primitives all returned values, then the user could (and must) write functions that return values; if all primitives expected continuations, then the user could (and must) write actors. Our interpreter provided both kinds of primitives, so it was possible to mix the two styles, which was our original objective.
> But the lambda and alpha mechanisms were themselves absolutely identical. We concluded that actors and closures were effectively the same concept.
> We were very pleased with this toy actor implementation and named it “Schemer” because we thought it might become another AI language in the tradition of Planner and Conniver. However, the ITS operating system had a 6-character limitation on file names and so the name was truncated to simply SCHEME and that name stuck. (Yes, the names “Planner” and “Conniver” also have more than six characters. Under ITS, their names were abbreviated to PLNR and CNVR. We can no longer remember why we chose SCHEME rather than SCHMR—maybe it just looked nicer.)
> then came a crucial discovery. Once we got the interpreter working correctly and had played with it for a while, writing small actors programs, we were astonished to discover that the program fragments in apply that implemented function application and actor invocation were identical! Further inspection of other parts of the interpreter, such as the code for creating functions and actors, confirmed this insight: the fact that functions were intended to return values and actors were not made no difference anywhere in their implementation. The difference lay purely in the primitives used in their bodies. If the underlying primitives all returned values, then the user could (and must) write functions that return values; if all primitives expected continuations, then the user could (and must) write actors. Our interpreter provided both kinds of primitives, so it was possible to mix the two styles, which was our original objective.
> But the lambda and alpha mechanisms were themselves absolutely identical. We concluded that actors and closures were effectively the same concept.