patr

The root patr comes from Latin pater (genitive patris) and its Greek twin patēr — both meaning "father." In the oldest Indo-European societies the father was not just a parent but the head of the household, the one who held property, made decisions, and represented the family to the outside world. That double sense — father as parent and father as authority — is the key to the whole family of words, because patr keeps drifting between the warm domestic meaning and the larger meaning of "the one in charge."

Start with the literal branch. paternal and paternity stay closest to home: paternal love, the paternal side of the family, a paternity test. The variant patern- is just pater worn down a little; patri- is the combining form that shows up before another element. From the same domestic core comes patrimony — patri (father) + -mony (a state or condition) — the property handed down from your father, your inheritance.

Now the authority branch. A patron was originally a Roman patronus: a powerful man who acted like a father toward people beneath him, protecting and supporting them in exchange for loyalty. That "fatherly protector" sense is why a patron today supports an artist or a cause — and why a patron of a shop is a regular customer it depends on. patronage is the support a patron gives. But the fatherly-superior posture has a dark side: to patronize someone can also mean to treat them like a child, talking down from a height — the protective father turned condescending.

Greek patēr gave us the "ruler" words. patriarch = patri (father) + -arch (ruler) = the father who rules a family or tribe; patriarchy is a whole society organized that way.

The most surprising leap is to country. To ancient Romans the patria was the "fatherland," the land of your fathers. So a patriot is literally someone loyal to the fatherland, patriotism is that loyalty, and the prefixes do the geography: ex- (out) + patria → expatriate, someone out of the fatherland; re- (back) + patria → repatriate, sending someone back to it; com- (together) + patria → compatriot, someone from the same fatherland.

One honest warning: pattern looks unrelated but actually belongs here — it came through Old French patron used in the sense of a "model" to copy (the way a patron sets the example), and only later split off in spelling and meaning. Two famous look-alikes do not belong: parent / grandparent come from Latin parere (to give birth), and parsimony / parsimonious come from parcere (to spare, be sparing) — neither has anything to do with pater.