Old English stybb "stump of a tree," from Proto-Germanic *stubjaz (source also of Middle Dutch stubbe, Old Norse stubbr), from PIE root *(s)teu- (1) "to push, stick, knock, beat" (see steep (adj.)). Extended 14c. to other short, thick, protruding things. Meaning "remaining part of something partially consumed" is from 1520s.
mid-15c., "dig up stumps, dig up by the roots," from stub (n.). The sens of "strike (one's toe) against" something projecting from a surface is first recorded 1848. Meaning "to extinguish a cigarette" is from 1927. Related: Stubbed; stubbing.
late 14c., of uncertain origin. Earliest form is stiborn. OED, Liberman doubt any connection with stub (n.). Related: Stubbornly; stubbornness.
late 14c., "thrust with a pointed weapon," first in Scottish English, apparently a dialectal variant of Scottish stob "to pierce, stab," from stob (n.), perhaps a variant of stub (n.) "stake, nail," but Barnhart finds this "doubtful." Figurative use, of emotions, etc., is from 1590s. Related: Stabbed; stabbing.