Boyd’s Bible Dictionary:
(kidneys). Once believed to be the seat of emotions; hence coupled with the heart (Psa. 7:9; 16:7; Jer. 17:10; 20:12).
“Loins” From Concise Bible Dictionary:
The part of man that is used to prefigure the seat of strength. Descendants are represented as coming out of the loins of a man (Gen. 35:11; Heb. 7:10). The loins were girded up for action and activity. God said to Job, “Gird up now thy loins like a man” (Job 38:3). In the Christian’s conflict with wicked spirits in the heavenlies he is exhorted to have his loins girt about with truth (Eph. 6:14).
“Reins” From Concise Bible Dictionary:
Human Kidneys
The kidneys, used symbolically for the inward thoughts and feelings (Psa. 7:9; Psa. 16:7; Psa. 26:2; Psa. 139:13; Prov. 23:16; Jer. 12:2; Jer. 17:10; Jer. 20:12; Lam. 3:13; Rev. 2:23). The word translated “reins” in Isaiah 11:5 is elsewhere translated “loins.”
Strong’s Dictionary of Hebrew Words:
Meaning:
from 2502 (in the sense of strength); only in the dual; the loins (as the seat of vigor)