Dictionary of Medieval Names
from European Sources

Leo m. Latin leo, Ancient Greek λέων 'lion'.

The name of 10 pre-1600 popes, six Byzantine emperors between the 5th and 10th C, an 8th C saint, and five kings of Armenia between the 12th and 14th C.

The name was often used by Jews, often as a translation of Hebrew Arye.

Brabant
Latin
1312 Leonii (gen) JeanIII p. 37
Czech Republic
Latin
1343 Leonis (gen) Rössler2 128, p. 65; 1345 Leoni (dat) CDEM-7.2 605; 1350 Leo (nom) Rössler1 53
Middle High German
1365 Lew (nom) Rössler1 58; 1373 Lew (nom) ibid. 102
England
Latin
1279–80 Leo (nom) WaHR-SK p. 30
Dutch
1593 Leon AuFr Busken; 1594 Lion ibid. Beusken; 1596 Leon ibid. Busken; 1599 Lion ibid. Busken
Early Modern English
1592 Lyon DEmar-vol2 p. 25
France
Latin
1049 Leo (nom) CartNDSaintes III; 1160 Leonis (gen) CartNDdOurscamp CXIV; 1378 Leoni (dat) hanquetvol1 1180, Leonii (gen) ibid. 2489, Leonio (dat) ibid. 521, Leonius (nom) ibid. 2489
Old French
1313 Lion Paris1313 p. 51
Germany
Latin
795x800 Leonis (gen) HambUrk-vol1 IV; 846 Leonis (gen) ibid. XI; 849 Leo (nom) ibid. XIII; 864 Leonis (gen) ibid. XVI; 920 Leonis (gen) ibid. XXIX; 937 Leo (nom) ibid. XXXIII; 1191 Leo (nom) quix-vol1 38; 1216 Leo (nom) hennes-vol1 25; 1401 leonio (dat) HD1401 no. 397
Italy
Latin
915 Leo (nom) RCI-Cam1 2, Leonis (gen) ibid. 2; 999 Leonem (acc) HGSav-4.1 p. 1, Leoni (dat) ibid. p. 1, Leonis (gen) ibid. p. 1; 1100 Leonem (acc) RCI-Cam1 627, Leoni (dat) ibid. 628; 1220 Leo (nom) hennes-vol1 49; 1224 Leo (nom) UrkRott-1 17; 1236 Leo (nom) TirNot1 9; 1282 Lione (nom) BBC-Berg p. XLVII; 1300 Leonis (gen) ActDipVeneto-I-1 p. 50; 1310 Leonus (nom) MonRav-2 CCCL; 1376 Leo (abl) DouGen1 p. 84, Leone (abl) ibid. p. 71; 1527 Leonis (gen) Rome1527 p. 87
Cite as: S.L. Uckelman. "Leo". In S.L. Uckelman, ed. The Dictionary of Medieval Names from European Sources, Edition 2016, no. 4. http://dmnes.org/2016/4/name/Leo.