Derivations of operation, operable vs. reparation, reparable

Question

After a little thought I decided irreparable derives from repairable, but a few seconds later, decided it stems from reparation, "like operable from operation". Looking the words up, I found I was wrong about both derivations:

Reparation and reparable derive from L. reparatus, pp. of reparare "restore", (ca. 1400 and 1570, resp.) rather than one from the other.

For operable and operation the story seems a bit different, with operable deriving in the 1640s from operate + -able and operation (late 1300's) from L. operationem, from pp. stem of operari.

What are the names of the processes by which these words derived from Latin?

Answer 1

I'm not sure you are interpreting those entries on Etymology.com the right way.

The Latin verb reparare ("to repair"), stem repara-, acquired the adjective reparabilis ("repairable"), regularly formed by the suffix -bilis in classical Latin. This then changed in French, a language which evolved naturally from Latin, into reparable during the 16th century. English borrowed this word again from French.

The past participle of reparare was regularly formed in classical Latin as reparatus ("[having been] repaired"), stem reparat-. In Late Latin, the action noun reparatio ("the repairing") was regularly formed from this by adding the action suffix -io, stem -ion-. The stem of this new action noun was (regularly) reparation-. In the 14th century, this word was borrowed by English (I suspect that it was also borrowed through French, but it doesn't say so).

The etymology of operable and operation is similar. Latin operari, stem opera-, leads to adjective operabilis (it doesn't say whether this word was actually formed in classical Latin, or in later Latin, or only hypothetically in successor languages), borrowed as operable in English ca. 1640.

Past participle stem opera-t-, leads to action noun operatio in Latin, borrowed/changed by French as operacion, borrowed by English from French as operation in the late 14th century.