Two of my favourite foods, together at last.
Samosa is from Hindi समोसा samosā, probably from a Persian form equivalent to Sanskrit sam plus bhuja and meaning "having equal sides". Samosas do have somewhat equal sides, if you make them right.
Sanskrit bhuja means "the side of any geometrical figure", but also "arm, branch, bough, bending, curve". The latter meanings let us trace it Proto-Indo-European *bheug- "to bend".
In Germanic, the variant form *bheugh- is found in Yiddish בייגל beygl, a diminutive formed from Old High German boug "ring". Bagels are vaguely ring-shaped, if you make them right.