sty (n.1)

"pen for pigs," Old English sti, stig "hall, pen" (as in sti-fearh "sty-pig"), from Proto-Germanic *stijan (source also of Old Norse stia "sty, kennel," Danish sti, Swedish stia "pen for swine, sheep, goats, etc.," Old High German stiga "pen for small cattle"). Meaning "filthy hovel" is from 1590s.

sty (n.2)

"inflamed swelling in the eyelid," 1610s, probably a back-formation from Middle English styany (as though sty on eye), mid-15c., from Old English stigend "sty," literally "riser," from present participle of stigan "go up, rise," from Proto-Germanic *stigan, from PIE root *steigh- "to stride, step, rise" (see stair).

sty (v.)

"go up, ascend" (obsolete), Old English stigan (past tense stah, past participle stigun, common Germanic (Old Norse, Old Frisian stiga, Middle Dutch stighen, Old Saxon, Old High German stigan, German steigen, Gothic steigan), from PIE root *steigh- "go, rise, stride, step, walk" (see stair).

updated on April 06, 2014

Definitions of sty from WordNet

sty (n.)
an infection of the sebaceous gland of the eyelid;
Synonyms: stye / hordeolum / eye infection
sty (n.)
a pen for swine;
Synonyms: pigsty / pigpen
Etymologies are not definitions. From, not affiliated with etymonline.