The word harass was taken as a loanword from French in the early 1600s. For a while, it was spelled with two letter rs, but by the eighteenth century almost everybody was just using one. It peaked in usage in literature in 1807 and has been decreasing since. The French verb it was taken from, harasser, could mean "to repeatedly attack", "to tire out", or "to devastate". Since it wasn't a very common word, that has a bit of an obscure origin, but etymologists think it's from harer, which meant "to set a dog upon". Harer, also thought to influence the word harry ("repeatedly attack"), is from Old Frankish hara, which meant "over here" (as in calling a dog somewhere), and that, through Proto-Germanic hi, derives from the Proto-Indo-European reconstruction ko, a demonstrative pronoun meaning "this".
Adam Aleksic, a rising sophomore studying linguistics and government at Harvard University, has been described as the internet's sixth most famous etymologist. He also has disturbing interests in politics, vexillology, geography, board games, conlanging, and law.