Let us pull out some roots.

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Obsequious has the latin root 'seqour means follow' in it. When a person is referred as Obsequious, he is full of following and servile.
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Querulous has the latin root 'queror means complain' in it. When a person is referred as Querulous, he is full of complaining and nagging.
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What can one think of the word Supercilious?
Super means above. Cilial refers to eye. Usually arrogance is accompanied by raised eye-brows(one that is above eye). A Supercilious nature can be linked to arrogance.
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Obstreperous means very noisy or boisterous. Because 'strepo means noise'.
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Impecunious, has its own story to tell us.
In olden days, a person's wealth is determined by counting the number of cattles, unlike counting shares and bank-balance.
One can get milk and meat from cattle, which is marked as true wealth.
'Pecus means cattle' in latin. Impecunious means one without cattle, which ultimately means, one without Wealth.
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