From Latin compositiōn-em "composition" via French. (Oxford English Dictionary)
In the sense of assigning the semantic values of complex expressions systematically or homomorphically from the semantic values of their parts, the words compositional and compositionality came into general usage among semanticists with their appearance in Katz and Fodor (1963):
Since the set of sentences is infinite and each sentence is a different concatenation of morphemes, the fact that a speaker can understand any sentence must mean that the way he understands sentences which he has never previously encountered is compositional: on the basis of his knowledge of the grammatical properties and the meanings of the morphemes of the language, the rules which the speaker knows enable him to determine the meaning of a novel sentence in terms of the manner in which the parts of the sentence are composed to form the whole. (pp. 171–172)
As a rule, the meaning of a word is a compositional function of the meanings of its parts, and we would like to be able to capture this compositionality. (pp. 191–192)
But as Pagin and Westerståhl (2011) point out, Hilary Putnam had already used the term compositional in essentially this sense, in a lecture delivered in 1960, but not published until 1975:
A mapping satisfying these (and suitable other conditions of the same kind) will be called a compositional mapping. Compositional mappings have the feature that their (value) for a compex sentence is a simple function of their value for related simple sentences. (For a natural, as opposed to an 'unnatural' language, the concept of a compositional mapping should be so defined that the range of a complex sentence should depend on the ranges of sentence of the kinds occurring in the 'derivational history' of the complex sentence....) (p. 77)
They note that Fodor was a student of Putnam's; so it seems very plausible that Katz and Fodor's use of compositional was based on Putnam's earlier use, and fair to credit Putnam as the source of the term.
Tracing the history of the concept of compositionality is a much more complex undertaking than tracing the origin of this use of the word, and well beyond the sort of thing I intend to do in this blog; but see Pagin and Westerståhl's article for a brief survey reaching back to medieval and classical sources.
References
- Katz, Jerrold J. and Jerry A. Fodor (1963) 'The Structure of a Semantic Theory', Language 39.2.170–210.
- Pagin, Peter and Dag Westerståhl (2011) 'Compositionality', in Claudia Maienborn, Klaus von Heusinger and Paul Portner (eds.), Semantics: An International Handbook of Natural Language Meaning, vol. 1, pp. 96–123. De Gruyter Mouton.
- Putnam, Hilary (1975). 'Do true assertions correspond to reality?', in Mind, Language and Reality: Philosophical Papers, Vol. 2., pp. 70–84. Cambridge University Press.