tough (adj.)

Old English toh "strong and firm in texture, tenacious, sticky," from Proto-Germanic *tanhu- (source also of Middle Low German tege, Middle Dutch taey, Dutch taai, Old High German zach, German zäh), which Watkins suggests is from PIE *denk- "to bite," from the notion of "holding fast." See rough for spelling change.

From c. 1200 as "strong, powerful;" c. 1300 as "not tender or fragile;" early 14c. as "difficult to chew," also "hard to endure." Figurative sense of "steadfast" is mid-14c.; that of "hard to do, trying, laborious" is from 1610s. Verb tough it "endure the experience" is first recorded 1830, American English. Tough guy attested from 1901. Tough-minded first recorded 1907 in William James. Tough luck first recorded 1912; tough shit, dismissive retort to a complaint, is from 1946.

tough (n.)

"street ruffian," 1866, American English, from tough (adj.).

Definitions of tough
tough (adj.)
not given to gentleness or sentimentality;
a tough character
tough (adj.)
very difficult; severely testing stamina or resolution;
the competition was tough
it's a tough life
it was a tough job
Synonyms: rugged
tough (adj.)
physically toughened;
the tough bottoms of his feet
Synonyms: toughened
tough (adj.)
substantially made or constructed;
some plastics are as tough as metal
a tough all-weather fabric
Synonyms: sturdy
tough (adj.)
violent and lawless;
tough street gangs
Synonyms: ruffianly
tough (adj.)
feeling physical discomfort or pain (`tough' is occasionally used colloquially for `bad');
he was feeling tough after a restless night
Synonyms: bad
tough (adj.)
resistant to cutting or chewing;
tough (adj.)
unfortunate or hard to bear;
a tough break
Synonyms: hard
tough (adj.)
making great mental demands; hard to comprehend or solve or believe;
Synonyms: baffling / elusive / knotty / problematic / problematical
tough (n.)
someone who learned to fight in the streets rather than being formally trained in the sport of boxing;
Synonyms: street fighter
tough (n.)
an aggressive and violent young criminal;
Synonyms: hood / hoodlum / goon / punk / thug / toughie / strong-armer
tough (n.)
a cruel and brutal fellow;
Synonyms: bully / hooligan / ruffian / roughneck / rowdy / yob / yobo / yobbo