The word loathe comes from Old English Lāþian ("to be hateful/displeasing").  It is derived from the adjective lāþ ("hated, hostile, repulsive"), which itself stems from Proto-Germanic Laitha- (hateful) and ultimately a Proto-Indo-European root Leit- (to detest).  It is related to words for sorrow or ugliness in German Leid, and Old Norse leið (hateful).  It is connected closely with "Loathe" (verb) developed from "loath" (adjective), which meant hostile or repulsive, while the adjective "loath" also came to mean reluctant.  It entered Middle English as lothen or lathien and the modern sense of intense disgust is attested by around 1200, with impersonal uses (e.g., "it loathes me") isn't common until the 16th century. 

The verb "loathe" (rhymes with clothe) was first used in English during the Old English period (pre-1150), according to the Oxford English Dictionary (OED).  The earliest known citation provided by the OED for the related adjective "loath" (rhymes with broth) comes from an anonymous work, the Poema Morale, from sometime before 1200.  

Examples of "loathe" used in a sentence: 
"They were rivals who truly and bitterly loathed each other."
"I loathe having to do this, but it is something that I can't ignore."
"It was a habit his wife loathed, but one he had trouble breaking."  
"She loathed the idea of being seen as a victim." 
"There is clearly much that he loathes about modern life." 
"Do you want to revamp your home but loathe the idea of spending your weekends painting walls?"