.To understand "Darmok and Jillad and Tanagra" Picard has to know the whos, whats, and whys of that phrase.
To grasp the full meaning perhaps, but to forge a basic understanding not so much. And & at are small words, but they provide sentence structure, and thereby context. Plus, that's one of the most basic examples. More often it's more descriptive or elaborated on, like when he 1st spoke...
Rai and Jiri at Lungha. (2 somethings or someones at somewhere)
Rai of Lowani. (The 1st is of something or somewhere)
Lowani under two moons. (Now we can guess it's a place)
Jiri of Ubaya. (The 2nd is from a different thing or place)
Ubaya of crossed roads. (Also now likely a place)
At Lungha. Lungha, her sky grey. (A 3rd place that they are both now at)
From the whole thing, we can extrapolate that Rai & Jiri are 2 beings that have come to a common place where neither of them originated. Rai comes from a place "under 2 moons". We could take that literally or based on the next phrase, assume it's figurative. Figuratively, it could mean several things, binary, split, being pulled in two directions etc... But the important idea is duality of some kind. Jiri comes from a place with "crossed roads". Figuratively, that seems to suggest divergent paths, or a place where a new direction can be taken, etc... Both these individuals, with their different figurative identities have come to the same place, that has a grey sky, a realm that is cloudy... Unclear
Dathon has described what they are doing there. They've come desiring a clarity be achieved between them. Maybe the Tamarians think they are like Jiri, from a place that's at a crossroads, ready to engage a new journey, and maybe they think the Federation is like Rai, from a place that has a duality. Maybe peaceful or maybe not. It's all right there
Now if Picard had tried to work with what he was hearing, they might have avoided the Darmok contingency. Then , once Darmok had begun, he was given a 2nd chance to understand what it was about, with the knife exchange. Had he done so, Dathon might not have had to die. He didn't even do a very good job of interpreting the gestures and body language. He was was deliberately written as dense, IMHO.
I mean what does the river Temarc likely do in winter? It stops running. Most of their phrases are descriptive like that