Concise Bible Dictionary:
Used typically for the source of nourishment. Israel “shall suck the breast of kings” (Isa. 60:16; compare Isa. 49:23; see also Job 24:9; Isa. 66:11).
Strong’s Dictionary of Hebrew Words:
Meaning:
from an unused root meaning apparently to contain; a receptacle (for milk, i.e. pail; figuratively, breast)