I see a lot of people in the lore sections here that quote direct passages from religiously biased books on accounts of creationism for races like it is absolute fact because it is in a book.

Author Ted Peterson, contract worker for Bethesda and author of:
From Morrowind
The Ancient Tales of the Dwemer; Fragment: On Artaeum; Mysticism, The Unfathomable Voyage; Notes on Racial Phylogeny; On Oblivion; The Old Ways; Origin of the Mages Guild; An Overview of Gods and Worship; Response to Bero's Speech; The Wild Elves; 2920; Biography of the Wolf Queen; Brief History of the Empire; Dance in Fire; The Firsthold Revolt; Galerion the Mystic; A Game At Dinner; How Orsinium Passed to the Orcs; The Madness of Pelagius; The Pig Children; The Wolf Queen; The Armorers' Challenge; The Axe Man; The Black Arrow; Bone; Breathing Water; The Cake and the Diamond; Chance's Folly; Feyfolken; The Final Lesson; The Four Suitors of Benitah; The Gold Ribbon of Merit; Hallgerd's Tale; A Hypothetical Treachery; Ice and Chitin; Incident in Necrom; Last Scabbard of Akrash; The Locked Room; Marksmanship Lesson; Master Zoaraym's Tale; The Mirror; The Mystery of Princess Talara; Night Falls on Sentinel; Palla; The Poison Song; Realizations of Acrobacy; The Rear Guard; Silence; Smuggler's Island; Surfeit of Thieves; The Third Door; Trap; Vernaccus and Bourlor; Withershins; The Wraith's Wedding Dowry; The Death Blow of Abernanit; The Horror of Castle Xyr; A Less Rude Song; Lord Jornibret's Last Dance; Cherim's Heart of Anequina; Invocation of Azura; The Charwich-Koniinge Letters; The Buying Game
From Daggerfall (some duplicate names)
Galerion the Mystic; The Madness of Pelagius; Ius, Animal God (regrettably); The Asylum Ball; A History of Daggerfall; Brief History of the Empire; The Fall of the Usurper; A Dubious Tale of the Crystal Tower; Banker's Bet; Healer's Tale; Jokes; Rude Song; The Arrowshot Woman; A Scholar's Guide to Nymphs; An Overview of Gods and Worship; Broken Diamonds; Confessions of a Thief; Etiquette with Rulers; Fragment: On Artaeum; Ghraewaj; Holidays of the Iliac Bay; Invocation of Azura; Legal Basics; Mysticism; On Oblivion; On Lycanthropy; Origin of the Mages Guild; Special Flora of Tamriel; The Alik'r; The Brothers of Darkness; The Faerie; The Old Ways; The Wild Elves; Vampires of the Iliac Bay; Wabbajack; The Pig Children; The War of Betony by Newgate; The War of Betony by Fav'te; Wayrest, Jewel of the Bay.

Ted Peterson:
"The origin of the "races", if that's even the proper term for them since many of them can interbreed, is largely speculative and based on myths and traditions. The corruption of the Orsimer is a popular explanation, but many in Tamriel consider them a beast race like the Argonians, thus the term "pig children". Of course, it's very difficult to separate scholarly research into the origin of species without social ramifications. It's a bit fuzzy, the differences between races anyhow. Bretons are considered one of the "man" races of Tamriel, but tradition has them with plenty of ancient mer blood in them. The Khajiit, considered a "beast race" now, may have some ancestors in common with the Mer as well, according to some traditions."
"Most people in Tamriel will say there are three main groups of elves -- the Bosmer, Dunmer, and Altmer. The less common strains of Ayleid, Maormer, Falmer, and others would also be considered part of the family. The Orsimer, even most charitably, would be considered a rather distant cousin."

I bring this up mostly to challange the idea by some that 'Words of Clan Mother Ahnissi" is absolute fact, or that there is a possibility the Orcs have always been orcs, and that creation of the races happened in a much more scientific method like evolution and cultural absorption as opposed to the religiously fanatical views of Gods hand crafting races for no other reason then they can. Like a lot of books in elder scrolls, they are written on purpose to be one sided or contradictory in nature to other accounts.
Example. In Words of Clan Mother, it very specifically lists members of the Nine Divine's in their creation story, yet the Khajiit were around long before the religion of the Nine Divines existed in Tamriel, this is simply a matter of cultural merging with Imperial interests and not a true to fact account of their creation.
So where is the hard proof that the Orc's were once elves, changed by the eating of Trinimac, and not always Orc's? Perhaps the story of Trinimac is used here to give the Orc's more acceptance by other races and the Empire but distancing themselves from a beast race, and presenting themselves in more of a mer light.