По Голдсмиту:
heraldry.sca.org/names/paul/sa.htmlPaul Goldschmidt's Dictionary of Period Russian Names - Section SASbyslav (m) -- "acquire glory."
◾Sbyslav Zhiroslavich, Russian warrior. 1171. [Tup 350]
◦Vars: Sbislaus. 1278. [Mor 172]
◾Sbislav. First Half of 12th Century. [Art VII 150; SR #9]
◾Sbizlai. 1276. [Mor 172]
◾Sbizlaus. 1267. [Mor 172]
◾Sobyslav. 13th-14th Century. [Art VII 14; #409]
◾Syslav. 13th Century. [Art VII 13; #407]
◦Pats: Sbyslavich (Eleufer Sbyslavich). 1268. [Mor 82]
heraldry.sca.org/names/paul/zpreface.html#MorещёList of Source Abbreviations Used
• AIG = Atlas istorii geograficheskikh otkrytii i issledovanii. Moscow: Glavnoe upravlenie geodezii i kartografii MVD SSSR, 1959.
• Art = Artsikhovskii, A. V., et al. Novgorodskie gramoty na bereste, Vols I-VII. Moscow: Izdatel'stvo Akademii Nauk SSSR, 1953-78. [#'s indicate birchbark accession numbers]
mirknig.com/knigi/guman_nauki/1181455109-novgor...
• Avr = Polnoe sobranie russkikh letopisei, Vol XVI: Letopisnyi sbornik, imenuemyi letopis'iu Avraamki, 1st edition. Saint Petersburg: Tipografiia F. Eleonskogo, 1889.
• Baz = Bazilevich, K. V., I. A. Golubtsov, and M. A. Zinov'ev. Atlas istorii SSSR, Chast' pervaia. Moscow: Glavnoe upravlenie geodezii i kartografii MVD SSSR, 1959.
• Buk = Bukharev, I. Zhitiia vsekh sviatykh. Moscow: Tipografiia Vysochaishe utverzhdennogo T-va I. D. Sytina, 1896.
• Che = Chew, Allan F. An Atlas of Russian History. New Haven CT: Yale University Press, 1967.
• Erm = Polnoe sobranie russkikh letopisei, Vol XXIII: Ermolinskaia letopis'. Saint Petersburg: Tipografiia M. A. Aleksandrova, 1910.
• Gil = Gilbert, Martin. Russian History Atlas. New York: Macmillan Co., 1972.
• Gra = Gramoty velikogo novgoroda i pskova. S. N. Valk, ed. Moscow: Izdatel'stvo Akademii Nauk SSSR, 1949.
• Ist = Map insert from: Istoriia kul'tury drevnei rusi. Domongol'skii period. I: Material'naia kul'tura. N. N. Voronin, M. K. Karger, and M. A. Tikhanova, eds. Moscow-Leningrad: Izdatel'stvo akademii nauk SSSR, 1948.
• Kaz = Polnoe sobranie russkikh letopisei, Vol XIX: Istoriia o kazanskom tsarstve (Kazanskii letopisets), 1st edition. Saint Petersburg: Tipografiia I.N. Skorokhodova, 1903.
• Khr = Polnoe sobranie russkikh letopisei, Vol XXII (Pt 2): Khronograf zapadno-russkoi redaktsii. Saint Petersburg: Tipografiia M. A. Aleksandrova, 1914.
• Lav = Polnoe sobranie russkikh letopisei, Vol I: Lavrent'evskaia letopis', 2nd edition. Leningrad: Izdatel'stvo Akademii Nauk SSSR, 1926/1962.
• Lev = Levin, Eve. Calendar of Saints -- 12th-15th Century Novgorod. Unpublished research notes from Russian and Bulgarian archives.
• Lvo = Polnoe sobranie russkikh letopisei, Vol XX: L'vovskaia letopis', 1st edition. Saint Petersburg: Tipografiia M. A. Aleksandrova, 1910.
• Mag = Magocsi, Paul Robert. Historical Atlas of East Central Europe. Seattle: University of Washington Press, 1993.
• Mai = Magocsi, Paul Robert. Ukraine: A Historical Atlas. Toronto: University of Toronto Press, 1985.
• Mor = Moroshkin, Mikhail. Slavianskii imenoslov ili sobranie slavianskikh lichnykh imen. Saint Petersburg: n.p., 1867.
mirknig.com/knigi/guman_nauki/1181439805-slavya...
• Nik = Polnoe sobranie russkikh letopisei, Vols IX-XIV: Patriarshaia ili Nikonovskaia letopis', 2nd edition. Leningrad: Izdatel'stvo Akademii Nauk SSSR, 1862-1910/1962.
• Nov = Polnoe sobranie russkikh letopisei, Vol IV: Novgorodskaia chetvertaia letopis', 1st edition. Petrograd: Tipografiia M. A. Aleksandrova, 1915.
• Red = Polnoe sobranie russkikh letopisei, Vol XXII (Pt 1): Khronograf redaktsii 1512 goda. Saint Petersburg: Tipografiia M. A. Aleksandrova, 1911.
• RIB = Russkaia istoricheskaia biblioteka. Saint Petersburg, 1875-1894.
• Ste = Polnoe sobranie russkikh letopisei, Vol XXI: Kniga stepannaia tsarskogo rodosloviia, 1st edition. Saint Petersburg: Tipografiia M. A. Aleksandrova, 1913.
• Tik = Tikhomirov, M. N. Drevnerusskie goroda, Second Edition. Moscow: Politicheskaia literatura, 1956.
• Tup = Tupikov, N. M. Slovar' drevne-russkikh lichnykh sobstvennykh imen. Saint Petersburg: Tipografiia I. N. Skorokhodova, 1903.
mirknig.com/knigi/nauka_ucheba/1181349178-slova...
• Ves = Veselovskii, S. B. Onomastikon. Moscow: Nauka, 1974.
• Zap = Polnoe sobranie russkikh letopisei, Vol XVII: Zapadnorusskaia letopisi, 1st edition. Saint Petersburg: Tipografiia M. A. Aleksandrova, 1907.
Ну, и ещё отсюда Сбыславы и Сбыславичи в новгородских летописях:
Сбыслав, новгородец - 6723 (54, 253, 446)
Сбыслав Степанович, новгородец - 6725 (57, 257)
Сбыслав Якунович (Якункович), новгородец - 6737 (68, 275), 6748 (293, 449)
Сбыслав Якунович (Якункович), посадн. Новгородский, XIII в. - 6497 (164), 472
Сбыслав - см. также Сбышка
Сбыславич, XIII в. - см. Алексей Сбыславич, Елевферий Сбыславич, Федор Сбыславич, Юрий Сбыславич
Сбышка Волосович, новгородец - 6702 (41, 234)
Сбышкинич, XIII в. - см. Юрий Сбышкинич
В общем, не сказать, чтобы имя было редким...