Freak
mid 16th century (in freak (sense 4 of the noun)): probably from a dialect word.
wiktionary
1560, "sudden change of mind, whim", of uncertain origin. Probably from a dialectal word related to Middle English frekynge(“capricious behaviour; whims”) and Middle English friken, frikien(“to move briskly or nimbly”), from Old English frician(“to leap, dance”), or Middle English frek(“insolent, daring”), from Old English frec(“desirous, greedy, eager, bold, daring”), from Proto-Germanic *frekaz, *frakaz(“hard, efficient, greedy, bold, audacious”) (in which case, it would be related to the noun under Etymology 2). Compare Old High German freh(“eager”), Old English frēcne(“dangerous”).
From Middle English freke, freike(“a bold man, warrior, man, creature”), from Old English freca(“a bold man, warrior, hero”), from Proto-Germanic *frekô(“an active or eager man, warrior, wolf”), from *frekaz(“active, bold, desirous, greedy”), from Proto-Indo-European *pereg-, *spereg-(“to shrug, be quick, twitch, splash, blast”). Cognate with Old Norse freki(“greedy or avaricious one, a wolf”), Old High German freh(“eager”), German frech, Old English frēcne(“dangerous, daring, courageous, bold”).
etymonline
freak (n.1)
1560s, "sudden and apparently causeless turn of mind," of unknown origin. Perhaps it is from a dialectal survival of a word related to Middle English friken "to move nimbly or briskly," from Old English frician "to dance" [OED, Barnhart]. There is a freking attested in mid-15c., apparently meaning "capricious behavior, whims." Or perhaps from Middle English frek "eager, zealous, bold, brave, fierce" (see freak (n.2)).
The sense of "capricious notion" (1560s) and that of "unusual thing, fancy" (1784) preceded that of "abnormally developed individual or production" (first attested in freak of nature, 1839, which later was popular in variety show advertisements for bearded ladies, albinos, etc.; compare Latin lusus naturæ, which was used in English from 1660s). As "drug user" (usually appended to the name of the drug) it attested by 1945. The sense in health freak', 'ecology freak, etc. is attested from 1908 (originally Kodak freak "a camera buff"). Freak show is attested from 1887.
freak (v.)
"change, distort," 1911, from freak (n.1). Earlier, "to streak or fleck randomly" (1630s). Related: Freaked; freaking.
freak (n.2)
"brave man, warrior," Scottish freik, from Middle English freke "a bold man, a warrior, a man," from Old English freca "bold man, a warrior," from frec "greedy, eager, bold" (compare German frech "bold, impudent").
