The noun form of "compute," referring to the amount or existence of computation, likely evolved through common usage and linguistic processes. The transformation of verbs into nouns is a common phenomenon in language, where the process is called nominalization.
In this case, the verb "compute" originally referred to the action of performing calculations or carrying out computations. Over time, as language evolves, it is common for verbs to take on nominal forms to express concepts or objects related to the action described by the verb.
The noun form "compute" emerged to describe the result or quantity of computational activity. This is similar to other verbs that have undergone nominalization, such as "calculate" becoming "calculation" or "write" becoming "writing."
Language evolves organically as speakers and writers adapt and repurpose words and their forms to suit their communicative needs. As a result, verbs can transform into nouns to express related concepts, leading to the creation of new words and linguistic structures in the process.