mugger(n = noun.person) - a robber who takes property by threatening or performing violence on the person who is robbed (usually on the street);
is a kind of robber
Derived form verb mug₁

   The common crocodile (Crocodilus palustris) of India, the East Indies, etc. It becomes twelve feet or more long. [Webster 1913 Suppl.]

   A thief who takes property by threatening (or performing) violence on the person who is robbed; a person who commits a mugging; one who mugs. See mug, v. t. [WordNet 1.5]

mugger, n. a broad-nosed Indian crocodile, Crocodylus palustris, venerated by many Hindus.

Etymology:
Hindi magar

N  evil doer, evil worker, wrongdoer, mischief-maker, marplot, oppressor, tyrant, destroyer, Vandal, iconoclast, firebrand, incendiary, fire bug, pyromaniac, anarchist, communist, terrorist, savage, brute, ruffian, barbarian, semibarbarian, caitiff, desperado, Apache, hoodlum, hood, plug-ugly, Red Skin, tough, Mohawk, Mo-hock, Mo-hawk, bludgeon man, bully, rough, hooligan, larrikin, dangerous classes, ugly customer, thief, cockatrice, scorpion, hornet, snake, viper, adder, snake in the grass, serpent, cobra, asp, rattlesnake, anaconda, canker-worm, wire-worm, locust, Colorado beetle, alacran, alligator, caymon, crocodile, mosquito, mugger, octopus, torpedo, bane, cutthroat, cannibal, anthropophagus, anthropophagist, bloodsucker, vampire, ogre, ghoul, gorilla, vulture, gyrfalcon, gerfalcon, wild beast, tiger, hyena, butcher, hangman, blood-hound, hell- hound, sleuth-hound, catamount, cougar, jaguar, puma, hag, hellhag, beldam, Jezebel, monster, fiend, devil incarnate, demon in human shape, Frankenstein's monster, harpy, siren, Furies, Eumenides, Hun, Attila, scourge of the human race, faenum habet in cornu.

hugger mugger