Douglas Harper's Etymology Dictionary
also freakout "bad psychedelic drug trip," or something comparable to one, 1966, from verbal phrase freak out, attested from 1965 in the drug sense (from 1902 in a sense "change, distort, come out of alignment"); see freak (n.). There is a coincidental appearance of the phrase in "Fanny Hill:"\n\nShe had had her freak out, and had pretty plentifully drowned her curiosity in a glut of pleasure ....
[Cleland, "Memoirs of a Woman of Pleasure," 1749]
\nwhere the sense is "she had concluded her prank."Wikipedia
Freak-Out is the seventh album released by the Japanese metal band Aion. This is the bands "softest sounding" album, the songs are more straight hard rock, with barely any metal edge to them. For this reason it is arguably considered the bands worst, reflected by them having disbanded the year of its release. Although not disbanded in the traditional sense, as Nov and Izumi continued to release their own music using the Aion name.
Usage examples of "freak-out".
Most heads are relatively careful about their drug diets, but in recent months the area has attracted so many young, inexperienced hippies that public freak-outs are a fairly routine thing.
The sidewalks are so crowded that even a mild freak-out is likely to cause a riot.