Arabic

bark- - skin of the belly of the camel and of the portion of the breast next to it; male breast (BK 1 116, Lane 193)

The additional meaning related to kneeling appears to be due to contamination with *bi/ark­ ‘knee’.

PWS
*barak- - chest, thorax (SED I No. 38)
Rather to be separated from *bi/ark- ‘knee’ (SED I No. 39). Note Akk. ‘lap’ in birku, burku [CAD b 255] given as a second meaning; this rather developed from the main meaning ‘knee’ (see *bi/ark­- ‘knee’), though it may also ensue from Sem. *barak-­ ‘chest’.