PS

*ˀir(r)-at- - chest, breast (SED I No. 9)

Akkadian
irtu - chest, breast (CAD I 183, AHw. 386)
Ugaritic
ˀirt - breast (DUL 110)
Tigre
ˀarra, pl. ˀarratat (poet. ˀaratat) - milt, by-stomach (of cattle) (WTS 357)
A semantic shift 'chest' > 'viscera' is quite common.