STY, an enclosed place or pen to keep pigs in. The word means properly a pen or enclosure for any domestic animal, as is seen from its occurrence in Scandinavian languages and in German, e.g. Swed. and Icel. slia, pen, gasstia, goose-pen, swinstia, pig-sty, Ger. Steige, hen-coop, Schweinsteige, pig-sty. It is usual to refer the word to stigan, to climb, which would connect it with stair and stile and with the Gr. arelxfiv. Some take the original meaning to be an enclosure raised on steps, others, in view of the Gr. VTOIXOS, row, would take the basic sense to be a row of pales or stakes forming a pen or enclosure; cf . the use of oroTxos for poles supporting nets to catch game in (Xen. Cyn. 6. ib). If the derivation from stigan is correct, the word is the same as that meaning a small inflamed swelling, tumour or abscess on the eyelid, the Old English word for which was stigend, i.e. short for stigend edge, a rising or swelling eye, hence in M. Eng. styang, taken as equivalent to "sty on eye."
Note - this article incorporates content from Encyclopaedia Britannica, Eleventh Edition, (1910-1911)