Иначе те двије фазе у насељавању су прилично добро објашњене на википедијином чланку Slavic settlement of the Eastern Alps,а преузете колико видим из више књига словеначких, њемачких и италијанских аутора:
"The first phase of Slavic settlement in the Eastern Alps region is dated around the year 550 and originated in the area of modern Moravia (i.e., the West Slavic speaking branch).[5] From there, Slavic peoples moved southward into the territory of the former Roman province of Noricum (modern Upper and Lower Austria regions). Subsequently, they progressed along the valleys of Alpine rivers towards the Karavanke range and towards the settlement of Poetovio (modern Ptuj), where the decline of the local diocese is recorded before 577.
The second phase of Slavic settlement came from the south and took place after the retreat of Lombards into Northern Italy in 568. The Lombards contracted to cede the relinquished territory to their new allies, the Avars, who at that time were the overlords of Slavs. Avars first appeared in Europe around 560 when they reached lower Danube. In 567 the Avars and Lombards jointly defeated the Gepids. After the Lombards moved to Italy in 568, the Avars became the nominal rulers of both the Pannonian plain (which they had conquered by 582) and the adjacent Eastern Alps region. The Slavic-Avar progress towards the Eastern Alps is traceable on the basis of synodal records of the Aquileian metropolitan church which speak of the decline of ancient dioceses (Emona, Celeia, Poetovio, Aguntum, Teurnia, Virunum, Scarabantia) in the respective area.[2][5][6] In 588 the Slavs reached the area of the Upper Sava River and in 591 they arrived to the Upper Drava region where they soon fought with the Bavarians who were led by king Tassilo I. In 592 the Bavarians won, but in 595 the Slavic-Avar army gained victory and thus consolidated the boundary between the Frankish and Avar territories. Between 599-600 the Slavs pushed through Istria and the Karst region towards Italy."
Мислим да је Y4882 добар кандидат за горе описану прву фазу.