I read once an article on the origin of "understand".

I have almost completely forgotten in now, but, at a stretch, it had something to do with an ancient custom (perhaps in the Roman senate?) of standing under the ensign of a senator in a show of approval and concurrence.

Does anyone recall? The correct explanation may prove me woefully off the mark, but that's a price I'm willing to pay.

it sound like a folk explaination..

but.. stan (as in pakistan, kazikstan..)is related to stand, and has the meaning of "we stand (are united) as one (people)
so the stan/stand meaning of being united or in concurrence does exist. interesting question.

Clark-Hall's Concise Anglo-Saxon Dictionary mentions the Latin subsistere suggesting it may have been a loan translation from the Latin.

Seems you're right.

Some of those folk etymologies are quite persuasive.

And the word substantive (as in the old-fashioned grammatical term noun substantive vs noun adjective)) comes from the same Latin verb. It's interesting that German has verstehen, rather than *unterstehen.

Not that verstehen makes any much more sense to the modern psyche than understand does. Are there any other cases of German ver- in place of Latin sub-?

Are there any other cases of German ver- in place of Latin sub-?

Not that I can think of at the moment. The prefix ver- is cognate with English for- and so started out as a kind of spatial verbal particle, like ueber- or unter; cf. English forbid, German verbietan. There is unternehmen (literally, 'to undertake') meaning 'to venture, wage'.

Those prefixed words most often resist explanation. The German unterstehen has at least 3 different meanings, which depend on whether the stress is on the 1st or the 3rd syllable. None, however, has anything to do with "understand". The German verb unternehmen can be literally translated: to undertake, but the corresponding noun das Unternehmen means "enterprise"..

As does the English noun undertaking.

So why are workers who handle the dead called undertakers?

It could simply be that 'underputters' was too awkward.