FRIEND, n. Fiend, misspelled and misinterpreted, usually until well after it is too late.
FRIENDSHIP: toxic contract in which it is agreed that one or more existential but personally inconvenient facts are to be ignored, nay actively denied, for the sake of a chancy companionship of dubious value and even more dubious longevity. See RELIGION. FAMILY: in which the toxic contract is inherited instead of being subjected to, voluntarily or otherwise, sometime after birth.
IGNORANCE: your refusal to ignore and deny existential facts in the matter agreed among my friends, thereby allowing me to classify you as a fiend and treat you accordingly.
In the ancient history of the English language (it says here), friend and fiend were considered to be opposites (“antonyms“, to use the $50 word). By the late 13th century CE, the word fiend had been sent to the Devil, and replaced by the word enemy, which had been stolen from France.
This might have been done to lessen confusion and reduce the number and severity of unfortunate incidents. Similarly, among sailors, the word larboard was replaced by the word port, lest people misunderstand commands and rush to the wrong side of the boat, with sad consequences.
It didn’t help.