hinterfotzig

Etymology
This term comes from southern Germany, a compound word created from and, the latter being derived from (regional). Therefore, the compound is an adjective for someone who is dishonest and likely to talk behind someone's back.

Adjective

 * 1) malicious, insidious, sneaky
 * 2) common, low, vulgar, mean

Adverb

 * 1) backwards
 * 2) from behind
 * 3) secretly, insidiously, stealthily