Languages change for extrinsic (heteronomous) reasons as well as intrinsic (autonomous) ones. A typical extrinsic cause of linguistic change is prestige. While all speakers generally are impelled to speak like their fellows, the spur to imitate the speech of others is particularly potent when prestige is involved.
This situation is true of institutionally regulated speech as well. Thus, in the recent past, speakers of British English (as heard, for instance on the BBC World Service) have largely converted to using the word sports in the plural rather than the traditional British English singular sport. This change can only be reckoned as resulting from the influence of American English (where sports is de rigueur), whose prestige has grown to such an extent that even speakers from the mother country must now bow to its status as the world language and change their idiolect accordingly. Autres temps, autres mœurs.
This morning I had to telephone the call center of a bank in order to transact some business. The voice that eventually got on the line sounded like a middle-aged woman who announced that she was speaking from South Dakota, so I said to her: “You sound like a native South Dakotan.” Her happiness was clearly audible: “Born and bred,” she answered, with a lilt in her voice, and repeated the phrase to punctuate her pride. “I’ve lived in South Dakota all my life! I’ve lived in the eastern part, and I’ve lived in the western part.” For my part, I said nothing about my being a linguist and being able to discern a South Dakota accent. (Listening to “Prairie Home Companion” for many years helped, of course, since Minnesotan and South Dakotan American English are similar.)
In an era when regional dialects are fading under the onslaught of media language, it is clear that natives of rural areas still cling tenaciously to their traditional linguistic forms of expression, and for them the fact that a stranger on the other end of the telephone line has acknowledged the authenticity of their speech is of considerable personal and social import.
The traditional name for the form of a noun when a member of this word class is used not just to name but to address someone or something is vocative. Together with the imperative of verbs, the vocative, strictly speaking, serves the so-called conative function. Thus the Indo-European languages (but not only) have to one or another extent maintained a vocative case and its concomitant separate desinence (ending) in the paradigm devoted to this naming or addressing function, although the overarching tendency in the history of these languages is for the vocative to fall together with the nominative in form. In a language like Russian, for instance, where the vocative overwhelmingly gave way to the nominative (except for the recent resurgence of the so-called “new vocative”), the form of the noun used for address is the same as the nominative, although Russian still has fossilized instances of the old vocative in religious terms like Боже (for nom. Бог ‘God’) and Господи (for nom. Господь ‘Lord’), which are now just part of common parlance as exclamations rather than terms of address.
Like any other language, English has a vocative intercalated in discourse that is identical in form with the nominative (subjective); moreover, as in all languages, English vocatives serve the phatic and emotive functions over and above the conative. A word like sir in military practice, for example, is a token of deference and is de rigueur in speech whenever a person of higher rank is addressed. This sort of practice can be called the “formulaic” use of the vocative, which also occurs in other contexts, such as in advertising and marketing, where agents who are serving customers or clients are encouraged to sprinkle their utterances with the addressees’ names (usually preceded by a term of deference such as “Mr.” or “Miss/Mrs./Ms.”).
A particular instance that is worthy of further study is the variable phatic and/or emotive use of the vocative as a feature of an individual speaker’s predilections when addressing an interlocutor. Speakers typically differ from each other in the frequency with which they resort to naming their interlocutors as part of discourse. Constant interspersion of one’s wife’s or husband’s name in addressing a spouse may start as a sign of endearment but may also ultimately devolve into a verbal tic devoid of emotive meaning and destructive of genuine affection. Similarly, the same speech habit in addressing a customer or client can easily lead to annoyance on the part of the addressee and subvert the very psychological affect that the utterer is aiming to engender in order to further their mercantile goal.