Syriac

geppā - wing; arm; fin; ell, fathom (LSyr. 128, SL 253)

PS
*gapp-, *ˀa-gapp- - wing (SED I No. 88)
There is a trend to compare this root with Sem. *gd/ḏp ‘to fly’ > *gadp- ‘wing’ implying a secondary formation with loss of *-d-, which is unlikely