r-ch-m — compassion; womb
ר.ח.ם (racham) ties compassion to the womb — rechem is a womb, rachamim is mercy, and they are the same three letters.
The word family
Every word below is built on ר.ח.ם. Same three letters, different vowels and prefixes.
Grammatically plural with no singular in normal use — Hebrew treats compassion as inherently multiple.
Standard Talmudic term for God, and the source of the Yiddish רחמנות (rakhmones), pity.
In the text
יְהוָה יְהוָה אֵל רַחוּם וְחַנּוּן
Adonai Adonai El rachum v'chanun
The LORD, the LORD, a God compassionate and gracious.
What I tell students about this root
This is the example I use when someone asks why roots matter. You can learn rachamim as a vocabulary item meaning mercy and never notice anything. Or you can see rechem inside it and understand that biblical Hebrew describes divine compassion with the word for a womb — a physical, maternal image sitting in the middle of the most quoted description of God in the Torah.