For a brief discussion on the sense of this rare word, see AF Gascony 68 and 69. An association with ‘apr. poderus, bdauph. pweyrus’ in the FEW (9,234b) seems likely.
a.
1powerful, mighty:
(
1323-25
)
Trescher e poeros seignur. A le vostre noble seignurie fatz assaver que je alay au chasteu de Sompuy [...]
91
poeros (1323-25)