Both, on both sides.
L. ambi "around, about," akin to Gk. amphi "around, about," Skt. abhi "on both sides," Av. aibi, aiwi, O.Pers. aiby "to, against, in addition to," Mid.Pers. aw-, ab-, Mod.Pers. af- (as in afzudan "to increase, add," afruxtan "to inflame, kindle, blaze," afqân "lamentation, groaning, cires for help"); O.H.G. umbi, O.E. ymb(e); PIE *ambhi- "around".
Ubâ- from O.Pers./Av. uba- (variants uva-, ava-, va-) "both," Skt. ubha "both," PIE *ubho(u); cf. Gk. ampho, L. ambo, Goth. bai, O.H.G. beide, Slav. oba, Lith. abhu.