See also: Tajik language
The 1911 Encyclopaedia Britannica wrote of Tajiks thus:
Tajik, or Parsiwan, a subject race of Afghanistan. Underlying the predominant Pathan elements in the country, the Tajik (Tajak, or Tausik) represents the original Persian possessor of the soil, who still speaks his mother tongue and therefore calls himself "Parsiwan". There are pure Persians in Afghanistan, such as the Kizilbashes of Kabul and the Naoshir-wanis of Kharan; but the name Tajik (= "stranger") appears to apply only to an admixture of original Arab and Persian stock, who are the slaves of the community - hewers of wood and drawers of water.
Everywhere the Tajiks are the cultivators in rural districts, and the shopkeepers and clerks in the towns. They are a fine, athletic people, generally fair in complexion, and assimilate in aspect, in dress, and much in manners to the Afghans, but they are never nomadic. The Tajik is as much the slave of the Pathan in Afghanistan as is the Hindki (whose origin is similar) in the plains of the Indus. Yet the Tajik population of the richly-cultivated districts north of Kabul proved themselves to be of good fighting material in the Afghan war of 1879-1880, and the few Kizilbashes that are to be found in the Indian army are brave soldiers. The number of the Tajiks in Afghanistan is estimated at 900,000.
The name itself originally occurs in the Pahlavi writings, and is explained to mean, first, the Arabs in general, then their descendants born in Persia and elsewhere out of Arabia, and, lastly, the Persians in general and their descendants born in Turkestan and elsewhere out of Persia. Tajik thus came to be the collective name of all communities of Iranian stock and Persian speech wherever found in Central Asia. These are co-extensive with the former eastward and northward limits of the Persian Empire; but, after the ascendancy of the Turkic races, they became the subject element in Turkestan, Afghanistan, Bokhara, Khiva, Kashgaria, while still politically dominant in Badakshan, Wakhan, Darwaz, Kost and Karateghin. In most of these places the Tajiks, with the kindred Galchas, seem to form the bulk of the population, the distinction being that "Tajik" applies rather to the settled and more civilized lowlanders of modern Persian speech, "Galcha" to the highlanders of Ferghana, Kohistan, Wakhan, &c., who speak either archaic forms of Persian or dialects intermediate between the Iranian and Sanskritic branches of the Indo-European linguistic family.
But, although mainly of Iranian stock, with light complexion and regular features, the Tajiks claim Arab descent, regarding the district about Baghdad as their primeval home, and considering themselves the descendants of the Arabs who overran Central Asia in the first century of the Hejira. At the same time, "it is evident that the inhabitants of the greater part of this region (Central Asia) must from an early period have come in contact with the successive waves of Turkish (Turki) and even Mongol population which broke over them; accordingly we find that, although the type is essentially Iranian, it has undergone a certain modification." (Capt. J. M. Trotter, Bokhara, p. 169). The term "Tajik" must be distinguished from "Sarte", the latter simply meaning "trader" or "shopkeeper," and being applied indiscriminately to the settled as opposed to the nomad element, and especially to the urban populations, of whatever race, in Central Asia.