I’ve encountered this phrase online and couldn’t find a dictionary definition for the phrase. What does “rank dishonesty” mean, and especially what does the word “rank” mean in this context?
According to a dictionary, ‘rank’ means ‘unpleasant’, ‘strongly’, or ‘extremely’ which are different from each other but all make sense in this context. I want to first confirm if this is a set phrase that has a idiomatic meaning beyond the literal one. Secondly, if it is not a set phrase, which meaning of ‘rank’ is the right one here?
(My first impression, which is very likely wrong, is it means someone with lower social/military rank being deliberately dishonest (backstabbing) against someone with a higher rank.)
To begin with, the noun rank has nothing to do with the adjective rank.
The noun is of French origin (possibly Frankish ultimately) and originally denoted a series or line of things (range has the same origin); then specifically a line of warriors or soldiers (whence our ‘rank and file’); then the successive lines, the first, second, third ranks, and so forth, in which soldiers are deployed; and finally, by way of one’s position in the front, middle or rear rank, one’s grade or standing.
The adjective rank is of Germanic origin; the precise line of descent is obscure but it seems originally to have denoted various attributes of the noble warrior: proud, haughty, rebellious, strong, vigorous, full-grown. In ME the martial connection faded and the word became used particularly of undesired and excessive strength, vigor and abundance; it was extended to vegetation (we still speak of ‘rank weeds’) and to loathsome behavior and smells (O mine offense is rank says Claudius); eventually it acquired such a strong negative connotation that came to mean ‘corrupt, foul, festering’, and eventually simply ‘extremely (offensive)’.
When your source writes of rank dishonesty it probably does not intend any one of these later senses but (at some level) all of them simultaneously: extremely gross, corrupt, loathsome dishonesty.