Among different types of language change, American English has had a long history of what has come to be called back-formation, that is “the creation of a new word by removing an affix from an already existing word, as vacuum clean from vacuum cleaner, or by removing what is mistakenly thought to be an affix, as pea from the earlier English plural pease.“(American Heritage Dictionary, 4th ed.). But this reduction of words is now being counter-balanced by engorged versions, in line with an opposite tendency, viz. toward hypertrophy, instanced here on several previous occasions.
Besides the verb commentate (< commentator) instead of comment, we now often have cohabitate (< cohabitation) instead of cohabit. This enlargement of the verb is given impetus by the relative frequency of its morphologically affiliated noun. In the case of cohabitate, ignorance of the normative verb is also doubtless a factor.
What may now seem like an isolated instance can be reevaluated as the instantiation of what the pioneering American linguist Edward Sapir called “drift”––alias the principle of final causation in language––and characterized as follows: “Wherever the human mind has worked collectively and unconsciously, it has striven for and attained unique form. The important point is that the evolution of form has a drift in one direction, that it seeks poise, and that it rests, relatively speaking, when it has found this poise.”
Present possibilities with greater or lesser powers of actualization exist at any given historical stage of a language. Innovations that come to be full-fledged social facts, i. e., changes, must have something about their form that enables them to survive. The aggregate of such innovations-become-changes is what constitutes the drift of a language. Items such as commentate and cohabitate are thus an early change of what can rightfully be reckoned a drift toward hypertrophy in American English.