Improbity

Origin of improbity (wickedness or dishonesty)

The English noun improbity comes from Latin improbitās (stem improbitāt-) "dishonesty, unscrupulousness," a derivative of improbus "inferior, improper."  The parts of improbus break down fairly easily: the prefix im- is a variant of the Latin negative prefix in- used before labial consonants (e.g., b, p) from the same Proto-Indo-European source as Germanic (English) un-, Greek a-, an-, and Sanskrit a-, an-.  The element pro- is from the very common (and complicated) Proto-Indo-European prefix and preposition per "forward, through, in front of, early, first."  The -bus is the same ending as in the Latin adjective superbus "proud, haughty" (the ultimate source of English superb) from the Proto-Indo-European root bheu- "to be, exist, grow," source of Germanic (English) be, Latin fuï "I was, have been" (the perfect of esse "to be"), and Slavic (Polish) być "to be."  The original sense of probus would be "going well, growing well," and improbus "not going well."  Improbity entered English in the late 16th century.

-- From dictionary.com