Loathsome

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Middle English: from archaic loath ‘disgust, loathing’ + -some1.

From Middle English lothsum, from Old English *lāþsum, from Proto-West Germanic *laiþsam, equivalent to loath +‎ -some. Cognate with Middle Low German lêtsam(“arduous”), German leidsam(“sad, sorry”).

loathsome (adj.)

c. 1300, "foul, detestable," from loath in its older, stronger sense + -some (1). Related: Loathsomely; loathsomeness.