Before and after the Roman invasion, successive waves of immigration passed over the Southern Uplands—Celtic Goidels, Celtic Brythons, Angles, Norsemen. The inhabitants prior to the first Celtic arrival are known as Iberians. Each wave of immigration influenced the populations and a striking result of this is seen in the place-names of Peebles and Selkirk. Gaelic and Cymric (i.e. British), English and Norse appear; Gaelic rare, Cymric common, while, since some roots are the same in English and Norse, the Norse element has perhaps been under-estimated. Gaelic are drum, cnoc, ra, as in Drummelzier, Knockknowes, Rachan; Cymric are caer, lin, pen, tor, tra, dre, as in Cardrona, Linton, Lee Pen, Torwood, Traquair, Dreva; common to Gaelic and Cymric are cad, loch, pol, as in Caddon, Polmood. Most of the river-names are Cymric, as Tweed, Fruid, Talla, Manor, Leithen, Yarrow, Tima. Cymric names are remarkable for their melody, as is clear from the rhythm of the following couplet formed of place-names in order of locality:

"Garlavin, Cardon, Cardrona, Caerlee,
Penvenna, Penvalla, Trahenna, Traquair."

English roots are ton, stead, cote, burgh, worth, heugh, law, edge, knowe, mount, head: Norse are grain (a branching river or river valley), scaur, myre, hope (valley), fell, rig (hill), holm, by. Sometimes a name has elements with the same meaning from different tongues—a sign of mixture of peoples—as Knockknowes (Celtic and English), Venlawhill (Celtic and two layers of English). Norse words in common use, now or formerly, are awns (spikes of barley), big (build), bygg (barley), gar, gimmer, leister, ling, lowe (flame).

This district being for centuries part of the Anglian kingdom of Northumbria, its language is descended from that form of Northern English which came to be known as Lowland Scots. While many linguistic features are common to Peebles and Selkirk, each shire has certain peculiarities of its own, which tend more and more to disappear. The Selkirk speech, however, is the more distinctive. The reason apparently is that Ettrick and Yarrow districts owing to their geographical situation were less affected by the speech of the Scottish Court, and therefore by English and French influences, than Peebles. Peebles belongs to the dialect division known as Eastern Mid-Lowland, and Selkirk to that known as South Lowland.

The Selkirk dialect, probably the most direct descendant of the old Anglian speech, is characterised by a great variety of diphthongs and by its softness and flexibility of intonation. The distinctions are as follows: final u tends to become a diphthong. Peeblesshire coo in Selkirk is nearer cuw or English cow. Words like see, me, we, he, dee (die) become sey, mey, wey, etc. Peebles "you an’ me ‘ll poo a pea" becomes in Selkirk "yow an’ mey ‘ll puy a pey." Words like bore and foal are diphthongized into buore and fuol; words like name, dale, tale are pronounced neb-um, deh-ul, teh-ul. When the diphthongs uo (or long vowel o) and ea occur at the beginning of a word or are preceded by h, the first develops into wu and the second into ye. Orchard is wurtshet; hole is hwull; whole is byel; oats is yetts; one is yin; earl is yen; home is hyem; sky is skyi; sword is pronounced with the w. Finally the South Lowland is distinguished by its broad pronunciation of the vowel in men, which sounds like a in man. Penny is thus pronounced like panny, while a as in battle is often pronounced as o in bottle: even educated persons sometimes pronounce a in English father as fother.

The total population of Scotland at the last census was 4,759,445, 2,307,603 males, and 2,451,842 females, or 106.2 females to 100 males. The figures for Peebles are: males 7067, females 8191, total 15,258 ; or 114.4 females to 100 males; and for Selkirk: males 11,332, females 13,268, or 117.08 females to 100 males. Peebles has 43.93 persons to the square mile. Only five counties have a less density. Selkirk has 91.82 persons to the square mile; and eighteen counties have a less density. The increase of the population within the last 100 years has been greatest in the case of Selkirk. This is due to the fact that it was at Galashiels and Selkirk that the Tweed industry had its origin, reaching its greatest development between 1861 and 1881.