Humus in Latin was soil (humilis being its adjective), and botanists who wrote about humble flowers were being descriptive rather than poetic; all they were saying was that such flowers grew close to the ground. But the other Latin meaning of humilis was different from any of ours. While humble's first meaning in English was "unassuming" (it was only later that it implied indigence as well), in Latin to be humilis was to be base, abject or mean, which shows the difference between the pagan and Christian cultures. The Romans had thought of humility as contemptible; Christians thought it virtuous. Cranmer translated the Greek tapeinos in the Magnificat as "humble and meek" although St Luke probably just meant "poor".
Such nuances matter little now, since the poor see no reason to be meek. Dickens did humble a disservice when he invented Uriah Heep, and bureaucrats made a nonsense of it by telling us they were humble servants. The old sense survives in humble pie, said by some to have been lately eaten in Florence, but this is a corruption of another word altogether - the now obsolete numbles, or deer's offal. I don't know whether it was ever served at 144 Coldharbour Lane.