The entry for Ukraine cites Room 2006, Placenames of the world, but his domain-specific knowledge seems to be lacking.
He also notes that “The territory was so called because it was the borderland or ‘frontier zone’ of medieval Russia at the time of the Tatar invasion in the 13th century.”
This is mixing up two different periods in history (and putting a Russian-centric spin on it). In fact the cities of Kyiv, Chernihiv, and Pereiaslav were the core territories (the so-called Rus land, Ruska zemlia) of medieval Kyivan Rus from the ninth century until its end when the Golden Horde sacked Kyiv in 1240. Indeed the name Ukraine is first attested in reference to this period in the Primary Chronicle (c. 1425), regarding the death of the prince of Pereiaslav in 1187, and regarding an 1189 expedition to Galicia, and it meant the surrounding territory that belonged to the respective principalities. (These were not “medieval Russia,” but the principalities of Rus, before the establishment of the Russian state.)
But the specific use of Ukraine (Ukraïna) for this country only goes back to the early modern period. It arose in Poland in the sixteenth century, when the ancestors of Ukrainians lived in a Polish–Lithuanian, not Russian, borderland country, and established the Cossack proto-state of Zaporizhzhia there in the 17th c.
As far as meaning, the early use of the term has been analysed with more than one possible relevant meaning, as “borderland,” as “country,” and as “foreign land.”
A good summary source is (esp. section 4):
- Alena Rudenka, “The ethnonymy and linguonymy of Belarusians and Ukrainians in the formation of their identity.” Onoma 58. doi 10.34158/ONOMA.58/2023/15
(The use of “Old Russian” for the Old East Slavic language is also archaic and biased.)