The title Ænima is a combination of the words 'anima' (Latin for 'soul' and associated with the ideas of "life force", and a term often used by psychologist Carl Jung) and 'enema', the medical procedure involving the injection of fluids into the rectum.

These segues are "Useful Idiot", "Message to Harry Manback", "Intermission", "Die Eier von Satan", "Cesaro Summability", and "(-) Ions".

The liner notes included references to dissociative anesthesia through ketamine as well as Timothy Leary, "futants", ritual magic, and religious fundamentalism.

[18] The inside cover displays art featuring a painting of a disabled patient that shows a resemblance to singer Maynard James Keenan and Bill Hicks depicted as a doctor or "healer" with the line, "Another Dead Hero".

Demo versions of the songs "Stinkfist", "Eulogy", "Pushit", and "Ænema" were recorded with Paul D'Amour on bass, before he left the band.

The person who left the message was a visiting Italian friend of Green Jellÿ member Gary Helsinger (known as "Hotsy Menshot").

[24] During Lollapalooza 1997, a version of "Hooker with a Penis" remixed by Billy Howerdel in the form of lounge music played over the public address system between sets.

It is introduced by a distorted bassline giving way to a heavy industrial guitar, starting at the :23 mark and lasting only ten seconds, playing a single chord in Drop C tuning over a reversed drum beat in 98 meter.

According to Blair McKenzie Blake, the maintainer of Tool's official website, "Die Eier von Satan" originally were cookies that "Marko Fox's grandmother used to bake for him as a child, without using eggs as an ingredient.

"[31] This magical incantation ("sim salabim bamba sala do saladim") is taken from the German children's song "Auf einem Baum ein Kuckuck" and popularized by Harry August Jansen.

An alternate version of "Pushit" was performed live, including an Aloke Dutta tabla solo, and appears on Salival.

The cover art and other images in the liner notes can be set behind the lenticular "lens" to create an effect of sequential animation.

European pressings of the CD featured a standard case, and the insert contained a catalog of sixteen fictional and humorously titled "other albums available by Tool".

The special images used for the lenticular effect are: Upon its release, Ænima was met with generally favorable reviews by mainstream music critics, citing the band's innovation and ambitions within the album's sound.

Jon Wiederhorn of Entertainment Weekly said that it was "one of 1996's strangest and strongest alt-metal records",[47] while USA Today's Edna Gundersen wrote that "Tool moves to the front of the alterna-metal shop on its third and best release".

[53] Los Angeles Times writer Sandy Masuo found that the band had successfully incorporated exotic instrumentation and sampling into their "raw, gripping rock" to give it "an even more exhilarating edge".

[49] David Fricke of Rolling Stone said that Tool "shove their iron-spike riffing and shock-therapy polemics right up the claustrophobic dead end of so-called alternative metal in the name of a greater metaphysical glory", calling the album "very admirable" and "even a bit impressive".

[54] In a retrospective review of Ænima, AllMusic writer Rob Theakston stated that on the album, "Tool explore the progressive rock territory previously forged by such bands as King Crimson.

The increasing density of their relentlessly downcast music, augmented by occasional electronic noises, begins to feel ponderous.

[57] All lyrics are written by Maynard James Keenan; all music is composed by Adam Jones, Danny Carey, and Justin Chancellor, unless otherwise noted[58]Samples