PROTO: *pina-ʁ-
MEANING: to strive, convenient, diligent, useful
RMEAN: стараться, пригодный, старательный, нужный
NEWCOM: The stem is confused with *pina-ʁ- 'to begin to melt, to break up (river), to overflow' and *pinaʁ- 'to be good (of weather)' in CED. REFER: 260